CCNA IP Routing Questions — Page 2 of 4

PBQmedium

You are connected to R1 via the console. R1 and R2 are running OSPFv2 in area 0. R1's router ID is 1.1.1.1, and R2's router ID is 2.2.2.2. Both routers are connected via GigabitEthernet0/0 on the 192.168.12.0/30 subnet. You need to ensure that R1 does not send OSPF hello messages out of its Loopback0 interface, while still advertising the loopback network into OSPF.

Network Topology

Hints

•The command is configured under the OSPF process.
•Use the keyword 'passive-interface' followed by the interface name.
•This prevents OSPF from sending hello messages on that interface.

A.Configure the passive-interface Loopback0 command under the OSPF process.

B.Remove the network 192.168.12.0 0.0.0.3 area 0 command from the OSPF configuration.

C.Configure the ip ospf passive-interface command on GigabitEthernet0/0.

D.Configure the network 192.168.12.0 0.0.0.3 area 0 command under the OSPF process.

AnswerA

solution

! R1
router ospf 1
passive-interface Loopback0

Why this answer

Configuring the Loopback0 interface as passive under the OSPF process suppresses the sending of hello messages on that interface, preventing unnecessary adjacencies. The network is still advertised because OSPF includes the subnet in its LSAs.

Exam trap

Trap: Candidates may confuse passive-interface with removing network statements or applying it to the wrong interface. Remember that passive-interface suppresses hellos but still advertises the network, and it should be applied to the interface that should not form adjacencies, not the transit link.

Why the other options are wrong

The specific factual error is that the network statement for the transit link is necessary for OSPF adjacency; removing it would break the OSPF neighbor relationship.

The specific factual error is that applying passive-interface to the transit link would prevent the OSPF neighbor relationship from forming, which is not the goal.

The specific factual error is that adding a network statement does not suppress hello messages; it only includes the interface in the OSPF process.

MCQmedium

A routing table entry begins with the code C. What does that code indicate?

A.A route learned through EIGRP

B.A connected network

C.A candidate default route

D.A static route to a classful network

AnswerB

The code 'C' in a Cisco IOS routing table represents a connected (directly attached) network. This entry is automatically generated when an interface has a valid IP address configured and is in the up/up state, and it carries an administrative distance of 0, meaning it is the most trustworthy source of routing information.

Why this answer

In Cisco routing table output, C indicates a directly connected network. These routes are installed when an interface is up and has an address in that subnet.

Exam trap

A frequent exam trap is mistaking the 'C' code for a static route or a route learned via a routing protocol like EIGRP. Some candidates incorrectly assume 'C' means candidate default or static, but Cisco IOS uses 'S' for static routes and 'D' for EIGRP-learned routes. Misreading these codes can lead to incorrect conclusions about how a route was learned or its trustworthiness.

Remember, 'C' always means the route is directly connected to the router, which is fundamental for understanding routing behavior and troubleshooting.

Why the other options are wrong

Option A is incorrect because EIGRP-learned routes are marked with 'D' in Cisco IOS routing tables, not 'C'. The letter 'D' stands for 'Dynamically learned' via EIGRP, so 'C' cannot represent EIGRP routes.

Option C is incorrect because candidate default routes are not indicated by 'C'. Cisco uses 'S*' or other notations for candidate default routes, so 'C' does not represent default routes.

Option D is incorrect because static routes use the code 'S' in Cisco routing tables. The code 'C' never represents static routes, so this option is invalid.

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MCQhard

Two routers are directly connected over IPv6 and should form an OSPFv3 adjacency, but they do not. Link-local addressing is present on both interfaces. Which issue is most likely to prevent the adjacency?

A.The interfaces are assigned to different OSPFv3 areas.

B.The routers need matching hostnames before OSPFv3 can start.

C.IPv6 requires a /64 only for routing protocols to function.

D.OSPFv3 cannot run on directly connected interfaces.

AnswerA

OSPFv3 requires that all routers on the same link share the same area ID; if one interface belongs to area 0 and the other to area 1, the Area ID field in the Hello packet doesn't match, and the packet is silently dropped. The neighbor state stays in DOWN because OSPFv3 cannot form an adjacency when the area numbers are different. This is a core OSPF principle: neighbors must be configured with the same area on the connecting link.

Why this answer

An area mismatch is a strong and direct explanation. In plain language, even though the routers can have valid IPv6 addressing and proper link-local communication on the interface, OSPFv3 still requires the two ends of the shared segment to agree on the area context for the adjacency. If one side places the interface in one area and the other side places it in another, the routers will not treat each other as valid neighbors.

This is very similar in principle to OSPF for IPv4. Link-local addressing matters in OSPFv3, but the protocol still enforces key neighbor-formation checks. The correct answer is the one that focuses on a required protocol match rather than on a vague issue like hostname or cable color.

Exam trap

Focus on OSPFv3 configuration requirements like area matching, not on distractors such as hostnames or prefix length.

Why the other options are wrong

OSPFv3 adjacency formation does not depend on hostnames; hostnames are only used for identification in show commands and have no impact on routing protocol operation.

OSPFv3 can use any valid IPv6 prefix length, including /64, /126, or /127, for the link between routers. The /64 requirement is for SLAAC, not for routing protocols.

OSPFv3 is specifically designed to run on directly connected interfaces, just like OSPFv2. It forms adjacencies over directly connected links to exchange routing information.

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MCQmedium

What problem is HSRP designed to solve?

A.Layer 2 switching loops

B.Loss of the default gateway if one router fails

C.Duplicate MAC addresses on trunks

D.Wireless interference

AnswerB

HSRP (Hot Standby Router Protocol) is a Cisco-proprietary First Hop Redundancy Protocol designed to eliminate the single point of failure that a default gateway represents. It allows two or more routers to share a virtual IP address and virtual MAC address, so hosts send traffic to the virtual gateway regardless of which physical router is active. If the active router fails or its upstream link goes down, the standby router assumes the virtual IP/MAC in seconds, preserving seamless connectivity to external networks.

Why this answer

HSRP provides a virtual default gateway so hosts continue forwarding traffic even if one physical gateway router fails.

Exam trap

Avoid confusing HSRP with load balancing or security protocols. Remember, HSRP is about redundancy, not traffic distribution or encryption.

Why the other options are wrong

Layer 2 switching loops are prevented by Spanning Tree Protocol (STP), not by HSRP. HSRP operates at Layer 3 to provide default gateway redundancy, not loop prevention.

Duplicate MAC addresses on trunks are typically caused by misconfigurations or bridging loops, not by HSRP. HSRP uses a virtual MAC address that is unique and does not cause duplication issues.

Wireless interference is a physical layer issue related to radio frequency signals, not something HSRP addresses. HSRP is a Layer 3 redundancy protocol for routers.

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MCQhard

Based on the exhibit, which route will be used to reach 172.20.10.33?

A.The static route to 172.20.10.32/27

B.The OSPF route to 172.20.10.0/24

C.The default route

D.No route, because the destination does not match any prefix.

AnswerA

This is correct because 172.20.10.33 falls in the more specific /27 prefix.

Why this answer

The route used will be the one with the longest matching prefix. In practical terms, 172.20.10.33 matches both the /24 and the /27 shown, but the /27 is more specific. That means the router selects the /27 route before considering the broader /24 or any default route.

This is exactly the kind of route-table interpretation the CCNA exam likes because it rewards precise thinking about prefix boundaries.

Exam trap

A common exam trap is to select the OSPF route or the default route instead of the static route with the longer prefix. Candidates often mistakenly believe that dynamic routing protocols like OSPF always take precedence or that default routes are used when any route exists. However, Cisco routers first evaluate the longest prefix match before considering administrative distance.

Ignoring this can lead to incorrect answers because the more specific /27 static route will always be preferred over the broader /24 OSPF route or the default route for the destination 172.20.10.33.

Why the other options are wrong

This option is incorrect because the OSPF route to 172.20.10.0/24 is less specific than the static /27 route. The router prefers the longer prefix match, so it will not use the /24 route when a /27 route exists.

The default route is not used here because there are more specific routes available that match the destination IP. Default routes only apply when no other matching routes exist.

This option is incorrect because the destination IP clearly matches both the /24 and /27 prefixes shown in the routing table. Therefore, the router does have routes to reach 172.20.10.33.

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MCQhard

Two OSPF routers connected on an Ethernet link remain in the INIT state. Which issue is the most likely cause?

A.The routers have identical router IDs

B.The routers cannot exchange Hellos bidirectionally on the segment

C.The routers have already reached FULL and are waiting to install routes

D.The routers are using the same OSPF process ID

AnswerB

In OSPF, the INIT state means that a router has received a Hello packet from a neighbor but did not find its own Router ID listed in that Hello, so bidirectional communication is not yet confirmed. This situation often arises from mismatched OSPF network types, incorrect subnet masks, or outbound/inbound Hello filtering on the Ethernet segment. Until both routers see each other's Router IDs in their respective Hello packets, they cannot proceed to 2-WAY and beyond, leaving the adjacency perpetually stuck in INIT.

Why this answer

INIT means a router is seeing Hellos from its neighbor but does not see its own router ID in the neighbor field of received Hellos. A common cause is one-way communication or a mismatched multicast/adjacency problem, often at Layer 2.

Exam trap

A common exam trap is to assume that duplicate router IDs cause routers to remain stuck in the INIT state. While duplicate router IDs do cause adjacency issues, they typically result in different neighbor states or error messages, not the INIT state specifically. Another trap is to think that using the same OSPF process ID on both routers causes adjacency failure; however, the process ID is locally significant and does not affect neighbor formation.

Misinterpreting the INIT state as a sign of routers already being fully adjacent or waiting to install routes is also incorrect, as FULL is a later state. The key is to recognize that INIT indicates one-way Hello communication, often due to Layer 2 or multicast issues.

Why the other options are wrong

Duplicate router IDs cause adjacency problems but usually result in neighbor states other than INIT or generate specific error messages. INIT state more commonly indicates one-way Hello communication rather than duplicate router ID issues.

Incorrect. FULL is the final OSPF neighbor state indicating full adjacency and route exchange completion. INIT is an early state and does not mean routers are waiting to install routes.

Incorrect. The OSPF process ID is locally significant and does not affect neighbor adjacency formation. Using the same or different process IDs on routers does not cause them to remain stuck in the INIT state.

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Drag & Dropmedium

Drag and drop the following steps into the correct order to configure a single-area OSPFv2 network on two Cisco routers (R1 and R2) and observe the neighbor state transitions from Down to Full.

Drag steps to the numbered slots on the right, or tap a step then tap a slot.

Steps

Order

1Step 1

2Step 2

3Step 3

4Step 4

Why this order

First configure OSPF process and router-id on R1, then add the network; repeat on R2; ensure interfaces are up; finally verify neighbor states to see the full transition sequence.

Exam trap

The trap is that candidates might think interfaces must be up before OSPF configuration, or that verification can be done after configuring only one router. The correct sequence ensures both routers are configured before checking neighbor states.

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Drag & Dropmedium

Drag and drop the following commands into the correct order to configure OSPFv3 for IPv6 on a Cisco router.

Drag steps to the numbered slots on the right, or tap a step then tap a slot.

Steps

Order

1Step 1

2Step 2

3Step 3

4Step 4

Why this order

Commands must be executed in order: global config, IPv6 routing, interface config, OSPFv3 on interface, then verification.

Exam trap

The most common trap is starting with the OSPFv3 router configuration command without first enabling IPv6 routing globally. Also, candidates may try to apply the interface-level OSPFv3 command before entering interface configuration mode.

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MCQhard

R1 and R2 are directly connected and running OSPF. The IP addressing is correct and both routers are in area 0, but they do not form an adjacency. What is the most likely cause?

A.The OSPF MTU values do not match on the connected interfaces.

B.The routers must use identical hostnames before OSPF can form neighbors.

C.The routers must use VLAN 1 for OSPF to operate.

D.The interfaces need to be configured as trunks instead of routed ports.

AnswerA

When OSPF neighbors exchange Database Description (DD) packets, each packet includes an interface MTU field. If the MTU values differ, the receiving router detects a mismatch and drops the DD packet, leaving the adjacency stuck in the ExStart or Exchange state. This prevents the routers from completing the database synchronization process, so the OSPF neighbor relationship cannot come up.

Why this answer

The most likely cause is an MTU mismatch between the two interfaces. During the OSPF database exchange process, neighbors must agree on the MTU value to successfully exchange DBD packets; a mismatch typically causes the adjacency to become stuck in the ExStart or Exchange state. Basic connectivity (e.g., ping) often still works because ICMP packets are small, but the OSPF adjacency fails due to the MTU discrepancy.

Exam trap

Don't overlook MTU settings when OSPF adjacency issues arise, especially when basic connectivity is confirmed.

Why the other options are wrong

OSPF neighbor formation does not depend on hostnames; it relies on matching parameters such as area ID, authentication, hello/dead intervals, and network type. Hostnames are only used for local identification and do not affect OSPF adjacency.

OSPF can operate over any VLAN or routed interface; there is no requirement to use VLAN 1. The adjacency issue is unrelated to VLAN numbering, and OSPF works independently of VLAN assignments on routed ports.

OSPF is designed to run on routed interfaces (Layer 3 interfaces) and does not require trunking. Trunk ports are used for carrying multiple VLANs between switches, not for OSPF adjacency between routers.

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MCQmedium

Why is route summarization often useful at distribution or area boundaries in larger networks?

A.It reduces the number of route advertisements by combining multiple specific prefixes

B.It forces all users into the same VLAN

C.It automatically encrypts routing protocols

D.It removes the need for IP addressing

AnswerA

At distribution or area boundaries, route summarisation aggregates multiple specific prefixes into a single, less specific advertisement, directly reducing the number of entries in the routing table and the volume of link-state or distance-vector updates. This satisfies the constraint of limiting control-plane overhead across the boundary, as fewer advertisements mean less processing and bandwidth consumption on routers at the summarisation point.

Why this answer

Route summarization is useful there because it reduces the number of specific prefixes that must be advertised upstream or across boundaries. In plain language, instead of sending many small route entries, the network can often advertise one broader summary that represents them collectively. This helps control routing-table growth and can make the design more scalable and easier to manage.

Summarization does not eliminate the need for routing detail inside the local area, but it can simplify what needs to be shared outward. That is why it is especially valuable at aggregation points such as distribution layers or area boundaries.

Exam trap

A common exam trap is selecting options that confuse route summarization with unrelated networking concepts such as VLAN design or encryption. For example, option B incorrectly states that summarization forces all users into the same VLAN, which is false because VLANs are Layer 2 constructs unrelated to routing summarization. Option C mistakenly associates summarization with automatic encryption of routing protocols, which is incorrect since encryption is a separate security feature.

Option D wrongly claims summarization removes the need for IP addressing, which is impossible because routing depends on IP addresses. Understanding that summarization only aggregates routing prefixes without altering VLANs, encryption, or IP addressing is essential to avoid these traps.

Why the other options are wrong

Incorrect because route summarization is a routing concept and does not influence VLAN membership or force users into the same VLAN, which is a Layer 2 function.

Incorrect because route summarization does not provide encryption; encryption of routing protocols is a separate security feature unrelated to summarization.

Incorrect because summarization does not remove the need for IP addressing; routing depends on IP addresses to forward packets correctly.

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MCQhard

A router learns 192.168.30.0/24 from OSPF and also has a static route to 192.168.30.0/24 with administrative distance 200. Which route is installed in the routing table while both are available?

A.The OSPF route

B.The static route

C.Both routes equally for load balancing

D.Neither route, because they conflict

AnswerA

OSPF has a default administrative distance of 110, while the static route was configured with an administrative distance of 200. Cisco routers always prefer the route with the lowest AD, so the OSPF route is installed in the routing table as the best path to 192.168.30.0/24. This is why the OSPF route is selected over the static route.

Why this answer

The OSPF route is installed because its default administrative distance of 110 is lower than the static route’s configured administrative distance of 200. In practical terms, the static route has been intentionally made a backup. It is present in the configuration, but it does not become active while the lower-distance OSPF route is healthy.

This is a classic floating-static design question. The important point is that route-source preference depends on administrative distance when the prefix length is the same.

Exam trap

A common exam trap is assuming that static routes always take precedence over dynamic routes because their default administrative distance is 1. In this question, the static route’s administrative distance is manually set to 200, which is higher than OSPF’s default 110. Many candidates mistakenly select the static route, overlooking that a higher administrative distance means lower preference.

This trap tests your understanding that administrative distance values can be adjusted to create floating static routes that serve as backups rather than primary routes.

Why the other options are wrong

Incorrect because the static route has a higher administrative distance (200) than OSPF (110), making it less preferred and preventing it from being installed while the OSPF route is available.

Incorrect because routers do not install multiple routes with different administrative distances to the same prefix simultaneously; only the route with the lowest administrative distance is installed.

Incorrect because routers can and do choose one preferred route when multiple routes to the same prefix exist; conflicting routes do not cause both to be rejected.

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MCQhard

A router receives two routes to 10.50.0.0/16: one from OSPF and one static route with an administrative distance of 90. Which route is installed by default?

A.The static route, because its administrative distance is lower than OSPF's

B.The OSPF route, because dynamic routes always override static routes

C.Both routes, because equal destination networks always load-balance

D.Neither route, because the destinations overlap

AnswerA

The static route is correct because its administrative distance is 90, which is lower than OSPF's default of 110. The router compares administrative distance values when multiple routing sources advertise the same prefix, and it installs the route with the lowest AD in the routing table. Since 90 is less than 110, the static route is preferred over the OSPF route.

Why this answer

By default, the static route with administrative distance 90 is installed because it is preferred over the OSPF route with default administrative distance 110. In plain language, the router is being told that the manually configured route is more trustworthy than the OSPF-learned one, so it chooses the static path first. The protocol type alone does not decide the outcome. Administrative distance is the key comparison when two different route sources offer the same destination prefix length.

This is a classic routing-selection question because many learners incorrectly assume OSPF always wins over static routes unless the static route uses the default administrative distance. Once the static route is given a value lower than OSPF’s 110, it becomes the preferred path unless a more specific route exists elsewhere.

Exam trap

A frequent exam trap is assuming that dynamic routing protocols like OSPF always override static routes regardless of administrative distance. Many candidates mistakenly believe that static routes only win if they use the default AD of 1. However, if a static route is manually assigned an AD lower than OSPF's default 110, it becomes the preferred route.

This misunderstanding leads to incorrect answers because the exam tests knowledge of how administrative distance influences route selection, not just the routing protocol type. Remember, the router always chooses the route with the lowest administrative distance, even if it is a static route with a custom AD.

Why the other options are wrong

Incorrect. Dynamic routes do not always override static routes; route preference depends on administrative distance, not just whether a route is dynamic or static.

Incorrect. Equal destination networks do not automatically cause load balancing if the routes have different administrative distances; only routes with equal AD and metrics are load-balanced.

Incorrect. Overlapping destinations from different sources are common and do not prevent route installation; the router uses administrative distance to choose the preferred route.

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MCQhard

A router has routes to 192.168.0.0/16 and 192.168.100.0/24. Which route is used for traffic to 192.168.100.77?

A.192.168.0.0/16

B.192.168.100.0/24

C.Both routes are discarded because they overlap.

D.The default route is preferred if present.

AnswerB

The route 192.168.100.0/24 is selected because it has a longer prefix length (24 bits) than 192.168.0.0/16, and routers use the most specific matching prefix (longest prefix match) to forward traffic. For destination 192.168.100.77, the /24 route provides a more precise match, satisfying the constraint of optimal path selection based on subnet mask length.

Why this answer

The route to 192.168.100.0/24 is used because it is more specific. In plain language, even though the /16 route covers a large address range that includes the destination, the /24 route describes the destination network more precisely. Longest-prefix match therefore prefers the /24.

This is a basic but critical routing-table concept. The router does not choose the broader route when a narrower one matches the same destination.

Exam trap

A frequent exam trap is to select the broader route 192.168.0.0/16 because it seems to cover more addresses, including the destination. Candidates may mistakenly think that a larger subnet mask means a better route or that overlapping routes cause the router to discard both. However, Cisco routers always prefer the most specific route based on the longest-prefix match rule.

Overlapping routes are normal and do not cause discarding; instead, the router uses the route with the longest subnet mask. Misunderstanding this can lead to incorrect answers and confusion about routing behavior.

Why the other options are wrong

192.168.0.0/16 is a less specific route covering a larger address range. Although it includes 192.168.100.77, it is not chosen because a more specific route exists. Selecting this ignores the longest-prefix match rule.

Both routes are not discarded because overlapping routes are common in routing tables. The router uses the longest-prefix match to select the best route, so discarding overlapping routes is incorrect.

The default route is only preferred if no specific matching route exists. Since both 192.168.0.0/16 and 192.168.100.0/24 match the destination, the router chooses the more specific /24 route, not the default.

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MCQhard

A routing table contains these entries for the same destination space: 10.1.0.0/16, 10.1.10.0/24, and 0.0.0.0/0. Which route is used for traffic to 10.1.10.44?

A.10.1.0.0/16

B.10.1.10.0/24

C.0.0.0.0/0

D.No route, because the entries overlap

AnswerB

This is correct because 10.1.10.44 falls within that more specific prefix.

Why this answer

The 10.1.10.0/24 route is used because it is the most specific matching prefix. In plain language, even though the /16 route and the default route could also match, the /24 route describes the destination range more precisely. Longest-prefix match therefore selects the /24 entry.

This is a foundational route-selection rule. The default route remains important as a fallback, but it is not used when more specific routes exist. Likewise, the /16 route is less specific than the /24, so it loses for this destination.

Exam trap

A frequent exam trap is selecting the less specific route (10.1.0.0/16) or the default route (0.0.0.0/0) for the destination 10.1.10.44. Candidates might mistakenly believe that overlapping routes cause conflicts or that the default route overrides specific routes. However, Cisco routers always apply the longest-prefix match rule, choosing the most specific subnet mask that fits the destination IP.

Overlapping routes do not cause routing failures; instead, they provide multiple options where the router picks the best match. Misunderstanding this can lead to incorrect answers and confusion about routing behavior.

Why the other options are wrong

The 10.1.0.0/16 route is less specific than the 10.1.10.0/24 route. Although it matches the destination IP, the router prefers the more specific /24 prefix, so this option is incorrect.

The 0.0.0.0/0 default route is only used when no other specific route matches the destination. Since both /16 and /24 routes match, the default route is not chosen here, so this option is incorrect.

Overlapping routes like 10.1.0.0/16 and 10.1.10.0/24 are common and do not prevent routing. The router resolves overlaps by selecting the longest prefix, so this option is incorrect.

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PBQhard

You are connected to R1 via console. The network has a primary link to the ISP via R2 and a backup link via R3. Configure IPv4 and IPv6 floating static default routes on R1 so that the primary path goes through R2 (AD 1) and the backup through R3 (AD 10). Additionally, configure a static route on R1 for the internal LAN 192.168.10.0/24 via R2 (AD 1). The current configuration includes a static default route ip route 0.0.0.0 0.0.0.0 10.0.0.3, which causes a recursive routing failure because 10.0.0.3 is not a valid next-hop address. Identify and fix the issue, then apply the floating static routes.

Network Topology

Hints

•The IPv4 default route to 10.0.0.2 is missing from the routing table. Check if the next-hop is reachable via a directly connected interface.
•Remove the existing problematic static default route and reconfigure it with an explicit administrative distance of 1.
•For IPv6, use the ipv6 route command with the prefix ::/0 and specify the next-hop and administrative distance.

A.Remove the existing incorrect IPv4 static default route and reconfigure the primary IPv4 default route with the correct next-hop address (10.0.0.2) and AD 1. Add the backup IPv4 default route via 10.0.0.6 with AD 10. Then add IPv6 static default routes: ipv6 route ::/0 2001:DB8:1:1::2 1 and ipv6 route ::/0 2001:DB8:2:1::2 10. Also add the static route for 192.168.10.0/24 via 10.0.0.2 with AD 1.

B.Add a static route to 10.0.0.0/30 via the backup link to R3, then the default route to 10.0.0.2 will work. Then configure IPv6 default routes with AD 1 and 10 as described.

C.Change the administrative distance of the IPv4 default route to 10 and the backup to 1, so the backup becomes primary. Then configure IPv6 default routes with AD 10 and 1 respectively.

D.Remove the existing IPv4 static default route and configure it with the next-hop as the exit interface (e.g., GigabitEthernet0/0) instead of the IP address. Then add IPv6 default routes using the exit interface as well.

AnswerA

solution

! R1
no ip route 0.0.0.0 0.0.0.0 10.0.0.2
ip route 0.0.0.0 0.0.0.0 10.0.0.2 1
ipv6 route ::/0 2001:DB8:1:1::2 1
ipv6 route ::/0 2001:DB8:2:1::2 10

Why this answer

The IPv4 default route currently uses next-hop 10.0.0.3, which is not a valid address on any directly connected interface, causing a recursive lookup failure. Option A fixes this by removing the incorrect route and correctly adding the primary (10.0.0.2 with AD 1) and backup (10.0.0.6 with AD 10) default routes, fulfilling the floating static requirement. It also adds both IPv6 floating default routes and the LAN static route.

Option B is wrong because adding a route to 10.0.0.0/30 via R3 does not fix the next-hop 10.0.0.3 failure for the default route. Option C incorrectly reverses the administrative distances, making the backup path the primary. Option D erroneously uses an exit interface instead of the correct next-hop IP, which is not suitable for multi-access or point-to-point networks without additional configuration and does not resolve the original misconfigured next-hop.

Exam trap

Be careful: Recursive routing failure means the next-hop is not reachable. Check if the next-hop is directly connected and the interface is up. Do not confuse administrative distance with metric; lower AD is preferred.

Also, ensure IPv6 routes use the correct next-hop addresses and AD values.

Why the other options are wrong

Adding a static route to the backup link does not correct the invalid next-hop 10.0.0.3 used in the default route and fails to address the root cause of the recursive lookup failure.

Swapping the administrative distances makes the backup path preferred instead of the primary, violating the requirement that R2 be the primary with AD 1.

Configuring the default route with an exit interface rather than a next-hop IP can cause ARP resolution issues in broadcast networks and does not replace the incorrect next-hop 10.0.0.3.

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MCQhard

An engineer is troubleshooting an OSPF adjacency between two directly connected routers, R1 and R2. R1 is configured with a passive-interface default under the OSPF process, and the interface connecting to R2 is not explicitly set to no passive-interface. The engineer runs a show ip ospf neighbor command on R1 and sees no neighbors. What is the most likely reason for the missing adjacency?

A.The network statement does not match the interface IP address.

B.The passive-interface default command is preventing OSPF hellos on the interface.

C.The router-id is not configured, so OSPF cannot form an adjacency.

D.There is an OSPF authentication mismatch between R1 and R2.

AnswerB

The passive-interface default command configures OSPF so that every interface is passive unless explicitly overridden with 'no passive-interface'. A passive interface does not send OSPF hello packets, but the connected subnet is still advertised into the OSPF database. Without a 'no passive-interface' statement applied to the link between R1 and R2, neither router will send hellos, and an adjacency can never form—exactly matching the symptom of no neighbors.

Why this answer

The `passive-interface default` command under the OSPF process makes all interfaces passive by default, meaning OSPF Hellos are not sent unless explicitly overridden with `no passive-interface`. Since the interface to R2 was not configured with `no passive-interface`, R1 does not send Hellos, preventing adjacency. Option A is less likely because even if the network statement is correct, a passive interface still blocks Hellos.

Option C is incorrect because OSPF automatically selects a router-id if not configured (highest loopback or interface IP), and a missing router-id does not prevent Hellos. Option D is unsupported by the scenario; no authentication mismatch is indicated.

Exam trap

Cisco often tests the nuance that `passive-interface default` suppresses Hellos on all interfaces unless overridden, leading candidates to overlook the fact that even directly connected routers cannot form an adjacency without Hellos being sent.

Why the other options are wrong

The network statement 10.0.0.0 0.255.255.255 area 0 matches any IP in the 10.0.0.0/8 range, which likely includes the interface IP. Therefore, the network statement is not the issue.

A router-id is automatically selected from the highest loopback or physical interface IP if not manually configured. Lack of manual configuration does not prevent adjacency formation; OSPF will still function.

The running-config does not show any authentication configuration, and the symptom (no neighbors) is consistent with passive interfaces, not authentication mismatches. An authentication mismatch would typically show neighbors in EXSTART/EXCHANGE state, not missing entirely.

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Drag & Dropmedium

Drag and drop the following steps into the correct order to configure HSRP version 2 on an interface and ensure the router becomes the active router, then verify the HSRP state.

Drag steps to the numbered slots on the right, or tap a step then tap a slot.

Steps

Order

1Step 1

2Step 2

3Step 3

4Step 4

Why this order

The correct order for configuring HSRP version 2 to ensure the router becomes the active router is: first configure HSRP version 2 on the interface, then configure the HSRP group and virtual IP address, then set the HSRP priority to a higher value, then enable HSRP preempt, and finally verify using 'show standby'. Only option A follows this sequence. Options B, C, and D are incorrect because they place version after group, priority before version, or preempt before priority.

Exam trap

Candidates often place version configuration after group creation or set preempt before priority. Remember: version must be set before the group is created, priority before preempt.

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MCQhard

An OSPF router learns a route with metric 20 and another OSPF route to the same destination with metric 30. The prefix length is the same. Which path is preferred?

A.The route with metric 20

B.The route with metric 30

C.Both routes are rejected because the metrics differ

D.The default route is preferred

AnswerA

OSPF uses a cost metric based on interface bandwidth, and lower cost indicates a more efficient path. When a router receives multiple OSPF routes to the same destination, it installs the route with the lowest metric into its routing table. Thus, the route with metric 20 is preferred because it offers a shorter or faster path than metric 30. This is standard OSPF path selection behavior, so the correct choice is the 20-metric route.

Why this answer

The OSPF path with metric 20 is preferred because, within the same routing protocol and for the same prefix length, the metric is used to compare candidate paths. In practical terms, the router is not comparing source trust here because both routes come from OSPF. It is comparing OSPF’s own internal path-cost values, and the lower metric wins.

This question is about separating administrative distance from metric. Since both routes come from the same protocol, metric is the deciding factor.

Exam trap

A common exam trap is confusing administrative distance with metric when comparing routes from the same protocol. Candidates might incorrectly think that a higher metric route is rejected or that administrative distance plays a role in choosing between two OSPF routes. In reality, OSPF always prefers the route with the lowest metric, and both routes remain valid candidates.

Misunderstanding this can lead to incorrect answers about route selection or route rejection, especially when multiple OSPF routes to the same prefix exist with different metrics.

Why the other options are wrong

This option is incorrect because a higher metric indicates a less preferred path in OSPF. The route with metric 30 is less optimal than the one with metric 20 and therefore not preferred.

This option is incorrect because OSPF does not reject routes simply because their metrics differ. Differing metrics are normal and help the router choose the best path rather than causing route rejection.

This option is incorrect because the router already has specific OSPF routes to the destination. A default route is not preferred when a more specific route with a valid metric exists.

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Multi-Selectmedium

Which TWO statements correctly describe the configuration and verification of OSPFv3 for IPv6?

Select 2 answers

A.OSPFv3 uses link-local IPv6 addresses to form neighbor adjacencies.

B.OSPFv3 uses global unicast IPv6 addresses to form neighbor adjacencies.

C.OSPFv3 is automatically enabled on all IPv6-enabled interfaces when the routing process is configured.

D.The 'show ospfv3 neighbor' command displays neighbor state, neighbor ID, and interface information.

E.The 'show ospfv3 neighbor' command displays the IPv6 address of the neighbor's interface as the neighbor ID.

AnswersA, D

When an OSPFv3 router sends Hello packets, it uses the IPv6 link-local address assigned to the outgoing interface as the source, and similarly for Database Description and other OSPFv3 packets. Because link-local addresses (FE80::/10) are valid only on the local segment and cannot be routed, they guarantee that OSPFv3 control traffic stays on that link. This design allows an adjacency to form even if the interface has no global IPv6 address configured.

Why this answer

OSPFv3 for IPv6 uses link-local IPv6 addresses (FE80::/10) to form neighbor adjacencies, not global unicast addresses (so B is incorrect). OSPFv3 does not automatically enable on all IPv6 interfaces; each interface must be explicitly configured under the OSPFv3 process using the 'ipv6 ospf' command (so C is incorrect). The 'show ospfv3 neighbor' command displays the neighbor's Router ID (a 32-bit value), not the IPv6 address of the neighbor's interface (so E is incorrect).

Correct options A and D accurately describe OSPFv3 neighbor formation using link-local addresses and the information shown by the 'show ospfv3 neighbor' command, which includes neighbor state, neighbor ID, and interface.

Exam trap

Cisco often tests the misconception that OSPFv3 behaves like OSPFv2 by using global unicast addresses for neighbor formation, or that enabling the OSPFv3 process automatically activates it on all interfaces, when in fact each interface must be explicitly enabled under the OSPFv3 process.

Why the other options are wrong

OSPFv3 uses link-local addresses, not global unicast addresses, for neighbor formation.

OSPFv3 requires explicit interface configuration under the routing process; it is not automatically enabled.

The neighbor ID shown is the Router ID, not the IPv6 address of the neighbor's interface.

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MCQhard

A router pair is directly connected, but they do not become OSPF neighbors. IP addressing and area assignment are correct. What is the most likely cause?

A.OSPF network type mismatch on the connected interfaces

B.Duplicate default routes on both routers

C.Missing VLAN trunking on the link

D.The OSPF process IDs are required to match

AnswerA

One side configured as point-to-point expects no DR/BDR election and often uses a different hello/dead interval, while the other side as broadcast conducts DR/BDR elections and relies on matching timers. This mismatch prevents the routers from reaching the two-way state, so they never form a stable adjacency even though the link is physically up.

Why this answer

OSPF network type mismatch is a frequent reason for adjacency failure when basic IP and area settings are correct. If one side is configured as broadcast and the other as point-to-point, the hello timers, neighbor discovery behavior, and designated router election rules diverge, preventing neighbor formation. Unlike process IDs (which are locally significant), a mismatch in network type directly affects how OSPF hellos are processed.

This is a well-known L2/L3 misconfiguration that must be checked alongside router‑ID and authentication parameters.

Exam trap

A common exam trap is assuming that OSPF process IDs must match on both routers to form neighbors. Many candidates mistakenly believe process IDs are globally significant, but they are only locally important identifiers. Another tempting mistake is blaming IP addressing or area mismatches without checking the OSPF network type.

Since network type controls how OSPF hellos are sent and received, a mismatch between broadcast and point-to-point types can silently block adjacency formation even when IP and area configurations appear correct. This subtlety often leads to confusion during troubleshooting and exam scenarios.

Why the other options are wrong

Incorrect because duplicate default routes affect routing decisions but do not impact the OSPF neighbor formation process, which depends on hello packets and network type compatibility.

Incorrect since VLAN trunking applies to Layer 2 switch ports, not routed interfaces running OSPF. The problem described involves OSPF adjacency, not VLAN or trunk configuration.

Incorrect because OSPF process IDs are locally significant identifiers and do not need to match between routers for neighbor relationships to form. This does not cause adjacency failure.

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PBQhard

You are connected to R1 via console. R1 must reach the remote loopback 2001:db8:1::1/128 on R3 via R2 (2001:db8:0:2::2/64). Currently, IPv6 ping fails. Additionally, configure a floating static default route via R2 (198.51.100.2/30) with an appropriate AD so that it only becomes active if a dynamic default route (with default AD 1) is absent. Identify and fix the recursive routing failure, correct the next-hop, set the correct AD, and ensure the default route is present.

Network Topology

Hints

•Check if the next-hop address is directly connected; use show ipv6 route to see if a recursive route exists.
•The default AD for a static route is 1; for a floating static route to back up a dynamic protocol, use a higher AD (e.g., 254).
•Use the exit interface in the static route to avoid recursive lookup failure.

A.Change the IPv6 static route to '2001:db8:1::1/128 GigabitEthernet0/1 2001:db8:0:2::2' and set the floating default route's AD to 254.

B.Change the IPv6 static route to '2001:db8:1::1/128 2001:db8:0:2::1' and set the floating default route's AD to 1.

C.Change the IPv6 static route to '2001:db8:1::1/128 GigabitEthernet0/1 2001:db8:0:2::2' and set the floating default route's AD to 1.

D.Change the IPv6 static route to '2001:db8:1::1/128 2001:db8:0:2::2' and set the floating default route's AD to 254.

AnswerA, D

solution

! R1
no ipv6 route 2001:db8:1::1/128 2001:db8:0:2::1
ipv6 route 2001:db8:1::1/128 GigabitEthernet0/1 2001:db8:0:2::2
no ip route 0.0.0.0 0.0.0.0 198.51.100.2 1
ip route 0.0.0.0 0.0.0.0 198.51.100.2 254

Why this answer

The original IPv6 static route uses the next-hop 2001:db8:0:2::1, which is R1's own G0/1 address, causing a routing loop. Correct the route by specifying a directly connected remote next-hop (2001:db8:0:2::2) either with or without the exit interface. Set the floating static default route with an AD higher than the dynamic route's default AD (e.g., 254) so it becomes a backup.

Option A (exit interface + next-hop) and Option D (next-hop only) both achieve this; Options B and C fail due to wrong next-hop or AD.

Exam trap

Be careful: using the router's own IP as a next-hop creates a forwarding loop, not a reachability failure. For a floating static route, the AD must be higher than the active route's AD to act as a backup.

Why the other options are wrong

The next-hop is R1's own address (loop) and AD 1 makes the route equally preferred to dynamic routes, defeating the floating purpose.

AD 1 makes the route equally preferred, not a floating backup.

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PBQhard

You are connected to R1. Configure OSPFv3 for IPv6 so that R1 and R2 can exchange IPv6 routes over their directly connected link. Enable IPv6 routing, assign OSPFv3 process and area on the interface, and verify that the neighbor adjacency forms and routes appear in the IPv6 routing table.

Network Topology

Hints

•OSPFv3 requires IPv6 unicast routing to be enabled globally.
•OSPFv3 is enabled on the interface, not under a router ospf process like OSPFv2.
•Use 'ipv6 ospf <process-id> area <area-id>' on the interface.

A.Enable IPv6 routing with 'ipv6 unicast-routing', configure OSPFv3 on the interface with 'ipv6 ospf 1 area 0', and verify with 'show ospfv3 neighbor' and 'show ipv6 route ospf'.

B.Enable IPv6 routing with 'ipv6 unicast-routing', configure OSPFv3 globally with 'router ospfv3 1' and 'router-id 1.1.1.1', then assign the interface to area 0 with 'ipv6 ospf 1 area 0'.

C.Enable IPv6 routing with 'ipv6 unicast-routing', configure OSPFv3 on the interface with 'ipv6 ospf 1 area 0', and verify with 'show ip ospf neighbor' and 'show ip route ospf'.

D.Enable IPv6 routing with 'ipv6 unicast-routing', configure OSPFv3 on the interface with 'ipv6 ospf 1 area 0', and verify with 'show ospfv3 neighbor' and 'show ipv6 route'.

AnswerA

solution

! R1
configure terminal
ipv6 unicast-routing
interface GigabitEthernet0/0
ipv6 ospf 1 area 0
end

Why this answer

It includes enabling IPv6 routing with 'ipv6 unicast-routing', applying OSPFv3 to the interface using 'ipv6 ospf 1 area 0', and verifying with the correct OSPFv3-specific commands 'show ospfv3 neighbor' and 'show ipv6 route ospf'. Option B is incorrect because it adds a global 'router ospfv3 1' command, which is unnecessary; OSPFv3 can be configured directly on the interface without a global process. Option C is incorrect because it uses IPv4 OSPF verification commands 'show ip ospf neighbor' and 'show ip route ospf', which are not valid for OSPFv3.

Option D is incorrect because although it uses the correct 'show ospfv3 neighbor', the 'show ipv6 route' command does not filter to OSPF-learned routes, so it displays all IPv6 routes rather than just OSPF routes.

Exam trap

Do not confuse OSPFv3 with OSPFv2. OSPFv3 uses 'ipv6 ospf' on the interface and 'show ospfv3 neighbor' for verification. Also, remember to enable IPv6 routing with 'ipv6 unicast-routing'.

Why the other options are wrong

Adding a global 'router ospfv3 1' command is unnecessary; OSPFv3 can be enabled directly on the interface without a separate global configuration.

Using 'show ip ospf neighbor' and 'show ip route ospf' are IPv4 OSPFv2 commands, not valid for OSPFv3 which requires 'show ospfv3 neighbor' and 'show ipv6 route ospf'.

The 'show ipv6 route' command displays all IPv6 routes, not just OSPF-learned ones; the filter 'ospf' is required to see OSPF routes specifically.

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MCQhard

A company wants to connect two sites across an IP network by creating a logical tunnel between the edge routers. Which technology is most directly associated with that requirement?

A.GRE

B.PortFast

C.DHCP relay

D.Root guard

AnswerA

Generic Routing Encapsulation (GRE) is a tunneling protocol that takes an entire packet and encapsulates it inside another IP packet, effectively creating a logical point-to-point link between two routers across an IP network. By configuring a GRE tunnel on each site's edge router, the two sites can exchange private addresses and routing information as if they were directly connected on the same link. This makes GRE a standard solution for site-to-site connectivity over IP networks, because it provides a simple, logical path for arbitrary payload traffic.

Why this answer

GRE is the most directly associated technology because it creates a logical tunnel between routers across an existing IP network. In practical terms, it allows the routers to treat the path as a virtual point-to-point connection for encapsulated traffic.

The question is specifically about tunneling between sites, not about plain routing, management, or switching behavior.

Exam trap

A common exam trap is mistaking GRE for unrelated Cisco features like PortFast or DHCP relay. PortFast is a Spanning Tree Protocol optimization for edge ports and does not create tunnels. DHCP relay forwards DHCP requests and is unrelated to site-to-site connectivity.

Another trap is confusing GRE with security features like IPsec; GRE itself does not encrypt traffic but only encapsulates it. Candidates might also overlook that GRE tunnels require proper MTU handling to avoid fragmentation issues, which can cause connectivity problems if ignored.

Why the other options are wrong

PortFast is incorrect because it is an STP feature that immediately transitions a switch port to forwarding state and does not provide any tunneling or routing capabilities.

DHCP relay is incorrect because it only forwards DHCP broadcast requests between clients and servers and does not create tunnels or connect sites logically over an IP network.

Root guard is incorrect because it is an STP topology protection feature that prevents a port from becoming a root port, and it does not create tunnels or affect routing.

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MCQhard

A network engineer adds a loopback interface Lo0 with IP address 172.16.0.1/32 to router R1. After restarting the OSPF process, the OSPF router-ID changes from 10.1.1.1 to 172.16.0.1, and the neighbor relationship with R2 resets. What should the technician do next to prevent this disruption the next time a loopback is added?

A.Configure passive-interface Lo0 under the OSPF process

B.Configure a static router-id using the router-id command under the OSPF process

C.Set a higher OSPF priority on the router’s interfaces

D.Configure the OSPF area as a stub area

AnswerB

The OSPF router-ID is dynamically derived from the highest loopback or active interface IP unless overridden. Creating another loopback with a numerically higher address would cause OSPF to adopt it as the new router-ID at the next process restart, tearing down every existing neighbor relationship. The `router-id` command forces the router to retain that fixed value indefinitely, because manually configured router-IDs take precedence over all IPv4/IPv6 interface addresses, making the network stable regardless of later loopback additions.

Why this answer

The OSPF router-ID is dynamically selected based on the highest IP address of any loopback interface, or if none exist, the highest IP of any physical interface. Adding a new loopback with a higher IP than the current router-ID causes OSPF to reselect a new router-ID upon process restart, which resets all neighbor adjacencies. Configuring a static router-ID with the 'router-id' command under the OSPF process prevents this disruption by fixing the router-ID regardless of interface IP changes.

Exam trap

Cisco often tests the misconception that adding a loopback interface automatically changes the OSPF router-ID immediately, but the trap here is that the router-ID only changes after an OSPF process restart or router reload, and candidates may incorrectly think passive-interface or priority settings can prevent the disruption.

Why the other options are wrong

Passive-interface does not influence router-ID selection, which is based solely on highest active loopback IP address at process initialization.

Confusing DR election parameters with router-ID election leads candidates to a parameter that is irrelevant to router-ID stability.

Changing area type does not address router-ID fluctuation; it targets LSDB optimization, which is unrelated to the dynamic router-ID re-election after loopback addition.

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100

MCQhard

An OSPF-enabled router R1 fails to advertise the 192.168.50.0/24 network to neighbor R2, even though the neighbor relationship is up. Which misconfiguration on R1 would cause this?

A.The OSPF process must be process ID 50 to advertise 192.168.50.0/24

B.The wildcard network statement does not match 192.168.50.0/24

C.OSPF cannot advertise a directly connected LAN

D.R2 needs a default route before learning intra-area routes

AnswerB

The OSPF network statement uses a wildcard mask that is the inverse of the interface's subnet mask. To advertise 192.168.50.0/24, the network statement must match that exact prefix, typically by using 192.168.50.0 0.0.0.255. If the wildcard mask is misconfigured—for example, 0.0.0.127 or 0.0.0.15—the interface will be excluded from the OSPF process, so R1 will not originate the route and R2 cannot learn it.

Why this answer

If the network statement on R1 does not match the interface connected to 192.168.50.0/24, OSPF will not enable on that interface and the subnet will not be advertised. The route stays absent from neighbors despite OSPF running elsewhere.

Exam trap

A frequent exam trap is believing that the OSPF process ID must match across routers to advertise specific networks or that OSPF cannot advertise directly connected LANs. Candidates may also incorrectly assume that a default route is required on a router before it can learn intra-area routes. These misconceptions lead to overlooking the actual cause: a mismatched wildcard mask in the network statement that prevents OSPF from activating on the interface.

This trap causes candidates to focus on irrelevant configuration elements instead of verifying the network statement accuracy.

Why the other options are wrong

The OSPF process ID is locally significant and does not affect which networks are advertised. Changing the process ID to 50 is unnecessary and does not solve the problem of missing routes.

OSPF can advertise directly connected LANs if their interfaces are included in the OSPF network statements. This option is incorrect because directly connected LANs are advertised when properly configured.

A default route is not required for a router to learn intra-area OSPF routes. OSPF routers exchange routing information through link-state advertisements without needing a default route first.

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101

MCQhard

Exhibit: A router has the following routes in its routing table: - OSPF: 10.1.1.0/24 - Static: 10.1.1.128/25 - Default: 0.0.0.0/0 A packet is destined for 10.1.1.130. Which route does the router use?

A.The OSPF 10.1.1.0/24 route

B.The static 10.1.1.128/25 route

C.The default route

D.The router load-balances across all three

AnswerB

Although the OSPF route has a lower administrative distance, the destination 10.1.1.130 falls inside the 10.1.1.128/25 range, and the forwarding decision uses longest-prefix-match: the /25 mask represents 128 addresses, while the /24 represents 256, making the /25 the most specific, or longest, prefix that contains the destination. Therefore, the router forwards this packet via the static route, not by any other attribute.

Why this answer

Routers use longest-prefix match before they think about metrics. The /25 route for 10.1.1.128/25 is more specific than the /24 or the default route, so traffic for 10.1.1.130 follows that path.

Exam trap

A common exam trap is to select a route based solely on routing protocol preference or administrative distance without considering prefix length. Many candidates incorrectly choose the OSPF 10.1.1.0/24 route because OSPF is a dynamic protocol and might assume it is preferred over a static route. However, Cisco routers always apply longest-prefix match first, so the static 10.1.1.128/25 route is chosen because it is more specific.

Another trap is to think the router load-balances across all routes, but load balancing only occurs among routes with equal prefix length and metric, not across different subnet sizes.

Why the other options are wrong

The OSPF 10.1.1.0/24 route matches the destination IP but has a shorter prefix length than the static /25 route. Since longest-prefix match takes priority, this route is not used.

The default route is a last-resort route used only when no other specific routes match the destination IP. Since more specific routes exist, it is not selected here.

The router does not load-balance across routes with different prefix lengths because longest-prefix match selects a single best route, so this option is incorrect.

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102

MCQeasy

Which Cisco IOS command configures a default static route pointing to next hop 203.0.113.1?

A.ip route 0.0.0.0 0.0.0.0 203.0.113.1

B.ip default-gateway 203.0.113.1

C.default-information originate 203.0.113.1

D.route add 0.0.0.0 203.0.113.1

AnswerA

The correct Cisco IOS command for a default static route is "ip route 0.0.0.0 0.0.0.0 203.0.113.1". The all-zero prefix and all-zero mask act as a wildcard, matching every destination IP address. Traffic with no more specific route matching in the routing table is forwarded to the next hop 203.0.113.1, establishing a default gateway for the router.

Why this answer

A default static route uses the all-zero network and mask, followed by the next-hop IP address or exit interface.

Exam trap

Remember that a default static route uses the all-zero network and mask, not a /32 mask or an exit interface unless specified.

Why the other options are wrong

The ip default-gateway command is used on Cisco switches in Layer 2 mode or on routers when IP routing is disabled. On a router with IP routing enabled, this command does not create a static route; it only sets the default gateway for the management interface, not for forwarding traffic.

The default-information originate command is used in routing protocols like OSPF or EIGRP to inject a default route into the routing domain. It does not create a static route itself; it only advertises an existing default route (which must already be present in the routing table) to other routers.

The route add command is used in Windows or Linux operating systems, not in Cisco IOS. Cisco IOS uses the ip route command to configure static routes. Using route add on a Cisco router would result in an unrecognized command error.

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103

MCQhard

A route to 10.10.20.0/24 disappears when an OSPF adjacency fails. Which design would most directly provide an automatic backup without changing the primary OSPF path during normal operation?

A.A floating static route with a higher administrative distance than OSPF

B.A standard static route with the default administrative distance of 1

C.Removing OSPF entirely and using only a default route

D.Disabling the routing table on the router until failure occurs

AnswerA

A floating static route is configured with an administrative distance greater than OSPF's default of 110 (commonly 120 or 150). Because the router prefers the lowest AD, this route stays out of the routing table while OSPF is healthy, but it is immediately installed when OSPF loses the route. This gives you a backup path without ever overriding OSPF's normal forwarding decision, which is exactly what a floating route is designed to do.

Why this answer

The most direct design is a floating static route with a higher administrative distance than OSPF. In plain language, that means the router keeps a manually configured backup route in reserve but does not use it while the OSPF route remains healthy. If the OSPF path disappears, the backup static route becomes active automatically. This is a very common and practical way to add simple failover.

The key requirement in the question is that the primary OSPF path should remain unchanged under normal conditions. A normal static route with default distance would override OSPF and break that goal. A floating static route avoids that by staying less preferred until a failure occurs. That is why it is the correct design choice here.

Exam trap

Avoid assuming that static routes are always less preferred than dynamic routes without considering administrative distance.

Why the other options are wrong

A standard static route with the default administrative distance of 1 would override the OSPF route (AD 110) because a lower AD is preferred. This would replace the primary OSPF path with the static route, not provide a backup that only activates upon failure.

Removing OSPF entirely eliminates the primary dynamic routing protocol, which is not a backup solution. The question requires preserving OSPF as the normal path and only providing an automatic backup when OSPF fails.

Disabling the routing table is not a valid operational practice; routers require the routing table to forward packets. This option does not provide any automatic backup mechanism and would break connectivity entirely.

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104

MCQmedium

Exhibit: R1 has a static default route to 192.0.2.2 and also learns a default route from OSPF. Which default route is installed in the routing table?

A.The OSPF default route because dynamic routes are preferred

B.The static default route because its administrative distance is lower

C.Both default routes because they have the same prefix length

D.Neither route until a floating static route is configured

AnswerB

Although both routes share the same /0 prefix, the static default route is installed because its administrative distance of 1 is far lower than OSPF's 110. The Cisco routing table uses AD to break ties between routes to the same destination learned from different protocols, and the lower the AD, the more trustworthy the source. Therefore, the static default route is selected and placed in the routing table, while the OSPF default route is not installed unless the static route fails.

Why this answer

When two routes to the same prefix are learned from different sources, the router compares administrative distance first. A static route has AD 1 by default, while OSPF has AD 110, so the static default route wins unless its AD was changed manually.

Exam trap

A common exam trap is believing that OSPF default routes always override static default routes because dynamic routing protocols are 'more intelligent' or 'preferred.' This misconception leads to selecting the OSPF route as installed, ignoring the fundamental Cisco routing rule that administrative distance determines route preference. Since static routes have a default AD of 1 and OSPF routes have an AD of 110, the static route is preferred unless its AD is manually changed. Misunderstanding this can cause incorrect answers and confusion about route installation behavior.

Why the other options are wrong

This option is incorrect because dynamic routes like OSPF are not automatically preferred over static routes. Administrative distance determines preference, and static routes have a lower AD than OSPF by default.

This option is incorrect because having the same prefix length does not mean both routes are installed. The router uses administrative distance to choose a single best route.

This option is incorrect because a normal static default route is valid and installed immediately. A floating static route is only needed if you want a backup route with a higher AD.

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105

PBQhard

You are connected to R1. Configure HSRP so that R1 becomes the active router for VLAN 10, with a virtual IP of 192.168.10.1. Ensure that R1 preempts if it comes back online after a failure. Also, configure R1 to decrement its HSRP priority by 20 if its GigabitEthernet0/1 interface goes down. The current configuration shows both routers as active — identify and fix the issues.

Network Topology

Hints

•Both routers show Active because they have equal priority and no preempt.
•The virtual IP configured is 192.168.10.254 but the task requires 192.168.10.1.
•To ensure R1 is active, set its priority higher than R2's default (100) and enable preempt.

A.Change the virtual IP to 192.168.10.1, set priority to 110, enable preempt, and track interface GigabitEthernet0/1 with decrement 20.

B.Change the virtual IP to 192.168.10.1, set priority to 100, enable preempt, and track interface GigabitEthernet0/1 with decrement 20.

C.Change the virtual IP to 192.168.10.254, set priority to 110, enable preempt, and track interface GigabitEthernet0/1 with decrement 20.

D.Change the virtual IP to 192.168.10.1, set priority to 110, enable preempt, but do not track any interface.

AnswerA

solution

! R1
interface GigabitEthernet0/0.10
standby 10 ip 192.168.10.1
standby 10 priority 110
standby 10 preempt
standby 10 track GigabitEthernet0/1 20

Why this answer

The scenario indicates both routers appear as Active, which is abnormal. This could result from a misconfigured virtual IP or group number mismatch. The required fix is to set the virtual IP to 192.168.10.1, assign R1 a higher priority (110 vs R2's default 100), enable preempt so R1 reclaims active role after failure, and track GigabitEthernet0/1 with a decrement of 20 to lower priority if that interface goes down.

Exam trap

Watch for three common mistakes: (1) forgetting to set a higher priority to win the election, (2) using the wrong virtual IP address, and (3) omitting the track command when required. Also note that preempt alone does not guarantee active status if priorities are equal.

Why the other options are wrong

HSRP election uses priority as the primary tie-breaker; equal priority leads to comparison of primary IP addresses, which may not favor R1.

The virtual IP address must be consistent across all HSRP routers and match the configured gateway; a mismatch prevents proper operation.

Without tracking, R1's priority remains unchanged even if the uplink fails, so R1 would remain active despite losing connectivity, causing traffic black-holing.

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106

MCQeasy

Which OSPF component is used to identify routers uniquely inside an OSPF domain?

A.Area ID

B.Router ID

C.Hello timer

D.Wildcard mask

AnswerB

The Router ID is a 32-bit value, typically derived from the highest loopback address or manually configured, that uniquely identifies an OSPF speaker within the autonomous system. It is carried in all OSPF packets and used as the originating router ID in LSAs, ensuring that each router is recognized as a distinct entity. Without a unique Router ID, OSPF neighbors could not reliably build a link-state database or exchange routing information.

Why this answer

The router ID is the unique identifier OSPF uses for each router. It is not the same thing as the process ID, which is locally significant only.

Exam trap

A frequent exam trap is mistaking the OSPF area ID for the router ID. While area IDs define logical groupings of routers within an OSPF domain, they do not uniquely identify individual routers. Another pitfall is confusing the router ID with the OSPF process ID, which is locally significant and does not uniquely identify routers.

Additionally, some candidates incorrectly select hello timers or wildcard masks, which serve different purposes such as neighbor keepalive intervals and network statement definitions, respectively. Understanding these distinctions is critical to avoid selecting incorrect options that sound related but serve different functions.

Why the other options are wrong

Area ID identifies OSPF areas, which are logical subdivisions within the OSPF domain, but it does not uniquely identify individual routers. Selecting area ID confuses the concept of router identification with area grouping.

Hello timer controls how often OSPF routers send hello packets to maintain neighbor adjacency. It does not serve as a unique identifier for routers.

Wildcard mask is used in OSPF network statements to specify which IP addresses belong to an OSPF area. It does not identify routers uniquely.

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107

MCQhard

Based on the exhibit, why is traffic to host 198.51.100.70 using the OSPF route instead of the static route?

A.Because the OSPF /26 route is more specific than the static /24 route.

B.Because OSPF always overrides static routing, regardless of prefix length.

C.Because the static route must have an administrative distance of 255 to be considered.

D.Because the destination 198.51.100.70 is outside both listed routes.

AnswerA

The OSPF route to 198.51.100.64/26 is chosen because it provides the longest prefix match for the destination 198.51.100.70, which falls within the .64 through .127 range. Although the static /24 route also contains this address, the /26 has more bits set in its network mask, making it more specific in the forwarding table. For traffic matching both a longer and a shorter prefix, routers always prefer the longer prefix, so the OSPF route is used.

Why this answer

The traffic uses the OSPF route because it is the more specific match. In practical terms, the router evaluates destination-prefix specificity before comparing route source preference. The static route points to a broader /24, while the OSPF entry points to a narrower /26 that still contains the destination. Because longest-prefix match comes first, the /26 route wins.

This is a good reminder that static routes do not automatically beat dynamic routes when the prefixes are different. Specificity matters first, then source preference only when the prefix length is the same.

Exam trap

A frequent exam trap is believing that static routes always take precedence over OSPF routes because static routes have a lower administrative distance. This misconception ignores the fundamental routing principle of longest-prefix match, which prioritizes the most specific subnet mask regardless of route source. Candidates may incorrectly select the static route simply because it is static, missing that the OSPF route’s /26 mask is more specific than the static /24.

This leads to incorrect answers and confusion about route selection behavior in Cisco routers.

Why the other options are wrong

Incorrect because OSPF does not always override static routes. Administrative distance matters only when prefix lengths are equal, and longest-prefix match takes precedence over route source.

Incorrect because the static route does not have an administrative distance of 255; it is valid and installed in the routing table. The issue is the static route’s broader prefix, not its administrative distance.

Incorrect because the destination IP 198.51.100.70 falls within both the /24 static route and the /26 OSPF route. The router chooses based on prefix specificity, not exclusion from the routes.

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108

MCQhard

What is the best explanation for why a router chooses the OSPF route to 10.50.0.0/16 instead of the RIP route?

A.Because OSPF has a lower administrative distance than RIP for the same prefix.

B.Because RIP routes are never installed when OSPF is running.

C.Because OSPF always has a longer prefix than RIP.

D.Because the RIP metric is lower than the OSPF metric.

AnswerA

Cisco IOS selects the route with the lowest administrative distance when multiple routing protocols offer the same destination and prefix length. OSPF's default administrative distance is 110, while RIP's is 120, so OSPF is considered more trustworthy and its route is installed in the routing table. Because both routes share the same /16 prefix, prefix length cannot break the tie, and the lower AD for OSPF becomes the decisive factor.

Why this answer

The router chooses the OSPF route because when the prefix length is the same, source preference is considered, and OSPF has a lower administrative distance than RIP. In practical terms, both routes describe the same destination size, so longest-prefix match does not separate them. The router then trusts the OSPF source more than RIP by default.

This is a classic administrative-distance comparison question and a very important route-selection concept.

Exam trap

A frequent exam trap is believing that RIP routes are never installed when OSPF is running or that the router always prefers the route with the lowest metric regardless of protocol. This is incorrect because RIP routes can remain in the routing table alongside OSPF routes. The router actually uses administrative distance, not metric, to choose between routes learned from different protocols.

Confusing metric with administrative distance leads to wrong answers, especially when both protocols advertise the same prefix length. Remember, cross-protocol route selection depends on administrative distance, not metric comparison.

Why the other options are wrong

Option B is incorrect because RIP routes can still be installed in the routing table even when OSPF is running; the router does not automatically suppress RIP routes.

Option C is wrong because both OSPF and RIP routes shown have the same prefix length (/16), so prefix length does not influence the choice here.

Option D is incorrect because cross-protocol route selection is based on administrative distance, not metric comparison; RIP's metric being lower does not make it preferred over OSPF.

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109

MCQmedium

Why is RIP rarely chosen for large modern enterprise networks?

A.It does not support IPv4

B.It scales poorly due to slow convergence and hop-count limitations

C.It cannot run on routers and only works on switches

D.It requires link-state advertisements

AnswerB

RIP's maximum hop count of 15 (with 16 considered unreachable) makes it impossible to use in networks with paths longer than 15 routers, and its distance-vector algorithm relies on periodic full-table updates and split horizon, causing slow convergence that scales poorly as network diameter grows. In large enterprise networks, route propagation and reconvergence times become unacceptably slow, and the hop limit itself is a hard scalability barrier.

Why this answer

RIP is simple but has important scalability limits, including a maximum metric of 15 and relatively slow convergence compared with more modern protocols such as OSPF and EIGRP.

Exam trap

Don't confuse RIP's limitations with features of other protocols; remember RIP's maximum hop count and distance-vector nature.

Why the other options are wrong

RIP supports both IPv4 and IPv6 (RIPng). The statement is factually incorrect because RIP has been used for IPv4 routing since its inception.

RIP is a routing protocol that runs on routers, not switches. While some multilayer switches can run routing protocols, RIP is not exclusive to switches.

RIP is a distance-vector protocol, not a link-state protocol. It uses hop count as its metric and exchanges entire routing tables, not link-state advertisements (LSAs) like OSPF.

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110

MCQmedium

Why is a default route often called a route of last resort?

A.Because it is used only when no more specific route matches the destination.

B.Because it always has the lowest bandwidth.

C.Because it must be learned from OSPF only.

D.Because it is more specific than every other route.

AnswerA

This is correct because the default route is a fallback path.

Why this answer

Ly identifies the default route as a route of last resort because it is used only when no more specific route matches the destination. Option B is incorrect because bandwidth is not a defining characteristic of a default route; it is simply a fallback path. Option C is wrong because default routes can be configured statically or learned via any routing protocol (e.g., OSPF, EIGRP, RIP), not exclusively OSPF.

Option D is false because the default route is the least specific route (0.0.0.0/0), not more specific than any other route.

Exam trap

A common exam trap is assuming the default route is learned only via OSPF or that it always has the lowest bandwidth, when in fact it is simply the least specific route used as a fallback.

Why the other options are wrong

Bandwidth is not a defining characteristic of a default route; the route is chosen based on prefix length and administrative distance, not bandwidth.

Default routes can be statically configured or learned from any routing protocol (including OSPF, EIGRP, RIP), so they are not OSPF-specific.

The default route (0.0.0.0/0) is the least specific route, not more specific; specificity is determined by the subnet mask length.

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111

MCQhard

Based on the exhibit, which command is the best next step to verify whether the floating static route becomes active after the primary route is lost?

A.show ip route

B.show vlan brief

C.show spanning-tree

D.show power inline

AnswerA

The 'show ip route' command is the correct next step because it displays the IPv4 routing table, directly showing whether the default route (0.0.0.0/0) has been installed. It will reveal the administrative distance and next-hop IP for both the primary and backup routes, allowing you to confirm if failover occurred after the primary route disappeared. This is the definitive way to verify routing-table state and default-route failover.

Why this answer

The best next step is to examine the routing table directly after removing or losing the primary route. In practical terms, the purpose of a floating static route is to appear when the better route disappears. The clearest way to verify that behavior is to inspect the route table for the default route after the failure condition.

This is a simulation-style verification question. It is not asking how to configure the route, but how to confirm failover actually happened.

Exam trap

A common exam trap is selecting commands unrelated to routing table verification, such as "show vlan brief" or "show spanning-tree." These commands provide information about VLAN configurations or Spanning Tree Protocol status but do not show whether a floating static route has become active. Candidates may mistakenly think these outputs indicate network failover status, but only the routing table output confirms if the backup route is installed after the primary route fails. Misunderstanding the purpose of these commands leads to incorrect answers.

Why the other options are wrong

"Show vlan brief" shows VLAN status and port assignments but does not provide any information about routing or route failover, so it cannot verify if the floating static route is active.

"Show spanning-tree" displays Spanning Tree Protocol information related to Layer 2 loop prevention, which is unrelated to routing table contents or route failover verification.

"Show power inline" displays Power over Ethernet (PoE) status and power consumption on switch ports, which has no relevance to routing or verifying floating static route activation.

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112

Drag & Dropmedium

Drag and drop the following steps into the correct order to explicitly configure OSPFv3 for IPv6 on a Cisco IOS-XE router, assuming no OSPFv3 routing process exists beforehand.

Drag steps to the numbered slots on the right, or tap a step then tap a slot.

Steps

Order

1Step 1

2Step 2

3Step 3

4Step 4

Why this order

To configure OSPFv3, first globally enable IPv6 unicast routing (A). Next, create the OSPFv3 routing process (C) so that it is defined before interfaces try to use it. Then, configure OSPFv3 on the relevant interfaces (B) to activate routing.

Finally, verify the OSPFv3 adjacency (D) to confirm neighbors are formed. This sequence avoids automatic process creation and ensures all steps are explicitly controlled.

Exam trap

Cisco exams often test the order of configuration steps. A common trap is to think that OSPFv3 interface configuration comes before creating the OSPFv3 process, or that verification can be done early. Remember that global IPv6 routing must be enabled first, as OSPFv3 depends on it.

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113

MCQhard

You are verifying OSPF operation on router R1. After confirming that OSPF is configured on the correct interfaces, which command should you use next to directly check whether R1 has established a neighbor adjacency with another OSPF router?

A.show ip ospf neighbor

B.show vlan brief

C.show spanning-tree

D.show mac address-table

AnswerA

show ip ospf neighbor is the correct next step because it directly lists all OSPF neighbors, their Router IDs, interface, and the current adjacency state (such as FULL/DR or 2WAY). This command verifies that the router has successfully formed an OSPF neighbor relationship and detects any state mismatches, making it the definitive tool for OSPF adjacency troubleshooting.

Why this answer

The command show ip ospf neighbor directly displays the OSPF neighbor table, showing whether an adjacency has formed, the neighbor's Router ID, and the current state (e.g., FULL). This is the quickest verification step after confirming configurations. The other commands are unrelated to OSPF: show vlan brief displays VLAN assignments, show spanning-tree shows STP topology, and show mac address-table shows the MAC address table.

None of these provide any OSPF neighbor information and would only delay troubleshooting.

Exam trap

Avoid confusing route visibility with neighbor status; they are related but distinct concepts.

Why the other options are wrong

Displays VLAN port membership; irrelevant to OSPF verification.

Shows STP topology; does not provide OSPF neighbor status.

Displays the switch's MAC address table; no OSPF information.

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114

MCQmedium

Exhibit: R1 can ping 10.1.23.2 but cannot ping 192.168.3.10 behind R3. The routing table on R1 lacks 192.168.3.0/24. What is the best next check?

A.Verify whether the remote LAN is being advertised into the routing process

B.Replace the Ethernet cable between R1 and R2

C.Change the OSPF router ID on R1 immediately

D.Disable CEF so the route can be learned

AnswerA

The symptom that R1 can ping the next-hop address 10.1.23.2 but not 192.168.3.10 indicates that reachability to the remote host is blocked at the routing layer, not the link layer. Since OSPF neighbors are up (the next hop responds), the most likely cause is that the subnet containing 192.168.3.10 is not being injected into the OSPF domain—either because there is no network statement under the OSPF process on the router that owns that LAN, because the interface is configured as passive-interface, or because an outbound distribute-list is filtering the route. Verifying the OSPF database for the 192.168.3.0/24 prefix directly confirms whether the route is being advertised.

Why this answer

Because the directly connected next router is reachable, the problem is likely missing routing information for the remote LAN. The best next check is whether R3 is advertising 192.168.3.0/24 or whether that network is present in the routing domain at all.

Exam trap

A frequent exam trap is to confuse physical connectivity with routing issues. Because R1 can ping 10.1.23.2 (likely the next-hop router), candidates might mistakenly try to fix cables or interfaces instead of checking routing advertisements. Another trap is to focus on router ID changes or disabling features like CEF, which do not affect route learning.

The key mistake is ignoring the routing table contents and assuming that reachability to the next-hop router guarantees full path reachability. This leads to wasted time and incorrect troubleshooting steps.

Why the other options are wrong

Replacing the Ethernet cable between R1 and R2 is unnecessary because R1 can already ping 10.1.23.2, indicating that the physical link and Layer 3 connectivity to the next-hop router are functioning correctly.

Changing the OSPF router ID on R1 is irrelevant here because the problem is not related to router ID conflicts or OSPF neighbor relationships but to missing route advertisements for the remote LAN.

Disabling CEF (Cisco Express Forwarding) will not help because CEF does not prevent routes from being learned or advertised; it only affects packet forwarding efficiency, so this option does not address the root cause.

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115

Multi-Selectmedium

Which two statements accurately describe longest-prefix match?

Select 2 answers

A.The most specific matching route is preferred over broader matching routes.

B.A /24 is more specific than a /16.

C.The default route is always preferred over a matching specific route.

D.Administrative distance replaces the need for longest-prefix match.

E.A /16 is more specific than a /24.

AnswersA, B

Longest-prefix match (LPM) is the fundamental forwarding decision rule used by routers: when multiple routing table entries match a destination IP address, the router chooses the route with the longest subnet mask, because that route identifies the smallest, most precise address range. This ensures that a host route (/32) or a /26 will always beat a less specific /16 or default route, guaranteeing predictable path selection toward the most exact destination.

Why this answer

Longest-prefix match means the router prefers the most specific route that matches the destination. In plain language, if several routes could all work, the router chooses the one that describes the destination range most precisely. That is why a /25 wins over a /24, and a /24 wins over a /16, when all of them match the same destination.

This is a foundational routing rule. The wrong answers usually confuse route specificity with route-source trust or assume the default route is considered first. The two correct answers are the ones that keep the focus on specificity.

Exam trap

A frequent exam trap is assuming that the default route (0.0.0.0/0) is preferred over more specific routes. Many candidates mistakenly believe the default route is always the first choice, but in reality, it is the least specific and only used when no other matching route exists. Another trap is confusing administrative distance with longest-prefix match; administrative distance only applies when choosing between routes learned from different sources, not when selecting the most specific prefix.

Misunderstanding these concepts can lead to incorrect answers about routing behavior in Cisco devices.

Why the other options are wrong

Option C is incorrect because the default route is the least specific and is only used when no other matching route exists, not preferred over specific routes.

Option D is incorrect as administrative distance is a separate concept used to select between routes from different protocols, not to replace longest-prefix match.

Option E is incorrect because a /16 is less specific than a /24; the longer the prefix length, the more specific the route.

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116

MCQhard

A network technician is troubleshooting a router-on-a-stick configuration. R1 has sub-interface G0/0.10 with encapsulation dot1q 10 and IP 192.168.10.1/24, and sub-interface G0/0.20 with encapsulation dot1q 20 and IP 192.168.20.1/24. Hosts in VLAN 10 cannot reach hosts in VLAN 20. The physical interface G0/0 is up and no shutdown. Both sub-interfaces show up/up. What should the technician do next?

A.Verify the switch port connected to R1 is configured as a trunk and allows VLANs 10 and 20.

B.Verify the encapsulation dot1Q numbers on the sub-interfaces match the VLAN assignments.

C.Verify the default gateway settings on hosts in VLANs 10 and 20.

D.Check the physical interface G0/0 for interface errors or duplex mismatches.

AnswerA

This directly addresses the most probable cause: a missing or misconfigured trunk on the switch side. Even with router sub-interfaces up/up, the link must be a trunk carrying the correct VLANs for inter-VLAN routing to function.

Why this answer

The router-on-a-stick configuration requires the switch port connecting to R1 to be configured as a trunk port that permits VLANs 10 and 20. Even though the router sub-interfaces are correctly configured with encapsulation dot1q and IP addresses, if the switch port is in access mode or does not allow the specific VLANs, frames from VLAN 10 or 20 will be dropped by the switch, preventing inter-VLAN routing. The next logical step is to verify the switch port configuration with commands like 'show interfaces trunk' or 'show running-config interface <port>'.

Exam trap

Cisco often tests the misconception that as long as the router sub-interfaces are up/up and have correct encapsulation, inter-VLAN routing should work, leading candidates to overlook the switch trunk configuration as the root cause.

Why the other options are wrong

Candidates may think the encapsulation numbers might be swapped, but the stem confirms they are correctly assigned to the respective VLAN IDs.

Many candidates jump to end-host configuration, assuming the router is fully reachable because interfaces are up/up, but the trunk is the prerequisite for any communication between VLANs.

Candidates might think any communication loss warrants a physical layer check, but here the symptoms point strongly toward a Layer 2 trunking issue.

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117

PBQhard

You are connected to R1. The network currently uses a static default route pointing to ISP1 (198.51.100.1) via GigabitEthernet0/0. However, the backup link to ISP2 (203.0.113.1) via Serial0/0/0 has a floating static default route with an administrative distance of 130. The backup route is not taking over when the primary link fails. Configure the floating static route correctly so that it becomes active when the primary route is lost, and verify that the routing table shows the backup default route with the appropriate next-hop.

Network Topology

Hints

•Examine the primary static route configuration for any unusual keywords.
•A static route with the 'permanent' keyword remains in the routing table even if the interface goes down.
•The floating static route has a higher AD (130) so it will only be used when the primary route is absent.

A.Remove the primary static route and reconfigure it without the 'permanent' keyword, then verify the backup route appears in the routing table.

B.Change the administrative distance of the floating static route to 1 so it is preferred over the primary route.

C.Add the 'permanent' keyword to the floating static route to ensure it remains in the routing table.

D.Configure a static route with a next-hop of 203.0.113.1 and an administrative distance of 130, but also add the 'track' command to monitor the primary link.

AnswerA

solution

! R1
conf t
no ip route 0.0.0.0 0.0.0.0 198.51.100.1 permanent
ip route 0.0.0.0 0.0.0.0 198.51.100.1
end

Why this answer

The primary static default route was configured with the 'permanent' keyword, which keeps the route in the routing table even when the GigabitEthernet0/0 interface goes down. This prevents the floating static route (AD 130) from becoming active. The solution is to remove the primary route (no ip route 0.0.0.0 0.0.0.0 198.51.100.1 permanent) and reconfigure it without the 'permanent' keyword.

After that, when the primary link fails, the route is removed, and the backup route (AD 130) enters the routing table. Option A is correct. Option B would make the backup preferred over the primary, which is not the intended behavior.

Option C (adding permanent to the backup) would not help and could cause issues. Option D (track) is an alternative but not the required configuration here.

Exam trap

Be careful: The 'permanent' keyword on a static route keeps it in the routing table even if the interface is down. This can prevent floating static routes from becoming active. Always check for 'permanent' when troubleshooting backup route issues.

Why the other options are wrong

The specific factual error: Administrative distance determines route preference; a lower AD is preferred. Setting the backup to AD 1 would make it the primary route, not a backup.

The specific factual error: The 'permanent' keyword prevents route removal when the interface goes down, which is not the solution here. The backup route needs to become active when the primary fails, not be forced to stay.

The specific factual error: The track command is used to conditionally remove a static route based on reachability, but it is not necessary if the primary route is correctly configured without 'permanent'. The existing backup route should work once the primary route is removed.

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118

MCQhard

Based on the exhibit, what is the most likely reason the PPP link is down?

A.The serial interfaces use different encapsulations.

B.PPP requires CAPWAP on both routers.

C.The routers must run BGP before PPP can establish.

D.Serial links can use only OSPF, not PPP.

AnswerA

PPP and HDLC are distinct Layer 2 encapsulation protocols for serial WAN links. Cisco default is HDLC; if one end is configured with encapsulation ppp and the other remains HDLC, the link cannot negotiate LCP or exchange frames, so the line protocol stays down. This mismatch is the most likely cause because the physical layer (Layer 1) is up but the data link cannot establish.

Why this answer

The PPP link is down because the two ends are configured for different encapsulations. In practical terms, one side is using PPP and the other is using HDLC, so the devices are not speaking the same data-link protocol on the serial link. Until those encapsulations match, the link cannot come up correctly at the data-link layer.

This is a classic WAN troubleshooting pattern that fits well into simulation-style exam coverage.

Exam trap

A frequent exam trap is to assume that routing protocols such as BGP or OSPF must be configured before a PPP link can establish, or that PPP requires additional protocols like CAPWAP. This is incorrect because PPP operates at Layer 2 and must first establish the data link before any routing protocol can function. Another common mistake is to believe that serial links cannot use PPP and only support OSPF or other routing protocols, which confuses encapsulation with routing.

The key is to recognize that mismatched encapsulation protocols like PPP versus HDLC prevent the link from coming up, regardless of routing configuration.

Why the other options are wrong

Incorrect because CAPWAP is a wireless protocol unrelated to serial link encapsulation. PPP does not require CAPWAP for operation on serial interfaces.

Incorrect because routing protocols like BGP are Layer 3 protocols and do not affect the Layer 2 establishment of a PPP link. The link must be up before routing protocols can run.

Incorrect because serial links can use PPP encapsulation. Cisco routers default to HDLC, but PPP is a supported and common WAN encapsulation protocol.

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119

MCQeasy

What metric does RIP use to choose the best path?

A.Bandwidth

B.Cost

C.Hop count

D.Delay

AnswerC

RIP (Routing Information Protocol) uses hop count as its sole metric, which is the number of routers (hops) a packet must traverse to reach the destination network. Each router that forwards the packet increments the hop count, and RIP considers a route with the fewest hops as the best path, regardless of link speed or reliability. This simple metric is why RIP is suitable for small networks but can choose suboptimal paths in larger, more complex topologies.

Why this answer

RIP uses hop count as its metric. Lower hop count paths are preferred, up to the protocol maximum of 15 usable hops.

Exam trap

Don't confuse RIP's hop count metric with metrics used by other protocols like OSPF or EIGRP.

Why the other options are wrong

RIP does not use bandwidth as a metric; it relies solely on hop count. Bandwidth is used by EIGRP in its composite metric calculation, not by RIP.

Cost is the metric used by OSPF, not RIP. RIP uses hop count as its sole metric, making cost an incorrect choice for this question.

Delay is not a metric used by RIP; RIP only considers hop count. Delay is a component in the EIGRP composite metric, but not in RIP.

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120

MCQhard

R1 and R2 are directly connected and running OSPF. They can ping each other, the area matches, and the timers match, but they still do not become neighbors. What is the most likely cause?

A.The OSPF authentication keys do not match.

B.The subnet mask is too small for OSPF to operate.

C.The routers must use different process IDs.

D.The interfaces must be configured as switch trunks.

AnswerA

This is the correct cause. In OSPF, if MD5 authentication is enabled but the configured authentication keys (or key IDs) do not match between the two routers, all OSPF hello packets are silently dropped. The routers remain reachable at Layer 3 via ping because IP forwarding does not depend on OSPF authentication, but they will never form a neighbor adjacency or exchange routing information.

Why this answer

The most likely cause is a mismatch in OSPF authentication keys. Even though the routers have IP connectivity, matching area IDs, and identical timers, OSPF adjacency requires that authentication parameters also match. If authentication is enabled on both sides but the keys differ, OSPF packets are silently rejected, preventing neighbor formation.

Exam trap

A frequent exam trap is to overlook OSPF authentication mismatches when routers have IP connectivity and matching area IDs. Candidates may incorrectly assume that because the routers can ping each other and timers match, adjacency must form. However, if OSPF authentication keys differ, routers silently reject OSPF packets, preventing neighbor formation.

This trap exploits the misconception that IP reachability alone ensures OSPF adjacency, ignoring the critical role of matching authentication parameters in the OSPF neighbor negotiation process.

Why the other options are wrong

This is incorrect because OSPF operates normally on /30 subnets commonly used for point-to-point links. Subnet mask size does not prevent OSPF adjacency.

This is incorrect because OSPF process IDs are locally significant identifiers and do not need to match between routers to form neighbors.

This is incorrect because OSPF runs over routed interfaces and does not require interfaces to be configured as switch trunks, which are used for VLAN tagging.

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121

MCQhard

A network administrator configures OSPF on two routers, R1 and R2, connected via their Serial0/0/0 interfaces (IP addresses 10.1.1.1/30 and 10.1.1.2/30). They verify that both routers use the same OSPF process ID and area 0, but R1's 'show ip ospf neighbor' shows no adjacencies. Given the partial exhibit from R1, what is the most likely cause of the adjacency failure and its correct solution?

A.Configure 'no passive-interface Serial0/0/0' under router ospf 1 on R1.

B.Replace the network statement with 'network 10.1.1.0 0.0.0.255 area 0' to cover a larger range.

C.Change the OSPF process ID on R1 to match R2, using 'router ospf 100' and re-entering the network command.

D.Issue 'clear ip ospf process' on R1 to restart OSPF and reattempt neighbor discovery.

AnswerA

In OSPF, the passive-interface command suppresses both outgoing and incoming Hello packets on the specified interface, so no neighbor relationship can be established on that link. Because Serial0/0/0 has been marked passive under the OSPF process, R1 never sends or processes Hellos even though the network statement includes that IP. Issuing no passive-interface Serial0/0/0 in router configuration mode re-enables Hello traffic on exactly that interface, allowing R1 and R2 to form a full OSPF adjacency. This is the only option that directly addresses the root cause of the missing neighbor.

Why this answer

The most likely cause is that R1's Serial0/0/0 interface is configured as a passive interface under OSPF. When an interface is set as passive, OSPF does not send Hello packets out of it, preventing neighbor discovery and adjacency formation. The solution is to use the 'no passive-interface Serial0/0/0' command under router ospf 1 on R1, which allows Hello packets to be transmitted and the adjacency to establish.

Exam trap

Cisco often tests the misconception that OSPF process IDs must match between routers, leading candidates to choose option C, when in fact process IDs are locally significant and only area IDs and authentication must match.

Why the other options are wrong

A larger wildcard mask does not override the passive-interface setting; adjacency still fails.

Adjacency depends on area and authentication, not on the router-local process ID; passive-interface is the real issue.

The root cause is a configuration that blocks hellos, not a transient state; the reset is ineffective.

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122

Multi-Selectmedium

Which TWO statements accurately describe OSPFv3 configuration and verification for IPv6?

Select 2 answers

A.OSPFv3 uses IPv6 link-local addresses for neighbor discovery and next-hop addresses.

B.The 'network' command under 'ipv6 router ospf' is used to advertise subnets into OSPFv3.

C.The 'ipv6 ospf <process-id> area <area-id>' command is used to enable OSPFv3 on an interface.

D.The 'ipv6 router ospf <process-id>' command is used on an interface to enable OSPFv3.

E.The 'show ipv6 ospf neighbor' command displays the OSPFv3 link-state database.

AnswersA, C

OSPFv3 routers build neighbor adjacencies and exchange hello packets using their IPv6 link-local addresses, so those addresses appear as the neighbor address and as the next hop for routes learned from that neighbor. On point-to-point and broadcast links, the link-local address is always used for forwarding to an adjacent router, even if global unicast addresses are also configured on the interface. This design lets OSPFv3 operate without depending on IPv4-mapped global addresses and avoids renumbering issues.

Why this answer

OSPFv3 uses IPv6 link-local addresses for neighbor discovery and next-hop addresses. Option C is correct because the 'ipv6 ospf <process-id> area <area-id>' interface command enables OSPFv3 on that interface. Option B is incorrect: OSPFv3 does not use the 'network' command; instead, it relies on interface-level configuration.

Option D is incorrect: 'ipv6 router ospf <process-id>' is a global configuration command to enter OSPFv3 router configuration mode, not an interface command. Option E is incorrect: 'show ipv6 ospf neighbor' displays neighbor adjacencies, not the link-state database; use 'show ipv6 ospf database' for that.

Exam trap

Cisco often tests the misconception that OSPFv3 uses the same 'network' command as OSPFv2, when in fact OSPFv3 requires interface-level configuration with the 'ipv6 ospf <process-id> area <area-id>' command.

Why the other options are wrong

'ipv6 router ospf <process-id>' is a global configuration command, not an interface command; enabling OSPFv3 on an interface requires the 'ipv6 ospf <process-id> area <area-id>' command.

'show ipv6 ospf neighbor' displays OSPFv3 neighbor adjacencies, not the link-state database; to view the LSDB, use 'show ipv6 ospf database'.

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123

Drag & Dropmedium

Drag and drop the following steps into the correct order to configure IPv4 and IPv6 static routes, a default route, and a floating static route with a higher administrative distance, then verify with show ip route and show ipv6 route.

Drag steps to the numbered slots on the right, or tap a step then tap a slot.

Steps

Order

1Step 1

2Step 2

3Step 3

4Step 4

Why this order

The correct order for configuring static routes as described is: first enter global configuration mode, then configure IPv4 static routes, then IPv6 static routes, then the default route and floating static route with higher AD, and finally verify with show commands. This sequence ensures that specific routes are configured before the default route and that IPv4 routes precede IPv6 routes as implied by the stem. Only option A follows this order; options B, C, and D deviate by placing the default/floating route before specific routes or configuring IPv6 before IPv4.

Exam trap

Do not confuse the order of configuration with the order of route preference. The default route is not configured first; it is configured after specific routes. Also, while IPv4 and IPv6 can be configured in any order, the question expects IPv4 before IPv6 based on the stem.

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124

MCQmedium

A router learns the same prefix from both OSPF and EIGRP. Which route is installed by default?

A.The OSPF route because OSPF is link-state

B.The EIGRP route because it has the lower administrative distance

C.The route with the lower metric value regardless of protocol

D.Both routes are always installed

AnswerB

The EIGRP route is installed because EIGRP has an administrative distance of 90, while OSPF uses 110. When a router receives the same prefix from different routing protocols, the lower AD is selected as the best path. Protocol-specific metrics are never compared across protocols; AD is the first tie-breaker.

Why this answer

When identical prefixes are learned from different routing protocols, the router compares administrative distance first. EIGRP internal routes use AD 90, while OSPF uses AD 110.

Exam trap

Remember that lower administrative distance values indicate higher preference. Don't confuse protocol complexity with route preference.

Why the other options are wrong

The type of routing protocol (link-state vs. distance vector) does not determine route preference when comparing routes from different protocols. Route selection is based on administrative distance, not protocol characteristics.

Metrics are only comparable within the same routing protocol. Different protocols use different metrics (e.g., OSPF uses cost, EIGRP uses composite metric), so they cannot be directly compared. Administrative distance is used to choose between protocols.

By default, a router installs only the best route (lowest AD) for a given prefix into the routing table. Both routes are not installed unless features like equal-cost multipath or policy routing are configured, which is not the case here.

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125

MCQhard

R1 and R2 are connected via a GigabitEthernet link in the same IPv4 subnet, and both routers have OSPF configured in the same area. However, R1 is not learning any OSPF routes from R2. What is the most likely cause?

A.GigabitEthernet0/0 is configured as a passive OSPF interface on R1.

B.The routers must use different OSPF process IDs to exchange routes.

C.The routers are in different IPv4 subnets.

D.OSPF can advertise routes only across serial links.

AnswerA

GigabitEthernet0/0 being configured as a passive OSPF interface on R1 suppresses all OSPF hello packets on that link. Because R1 never sends hellos, it cannot establish a two-way neighbor relationship with R2; OSPF adjacency cannot form, and no OSPF routes are exchanged. This explains why R1 has no routes from R2 even though the physical link is operational.

Why this answer

The most likely reason is that one side has the interface configured as passive, which prevents OSPF hello packets from being sent on that interface. In practical terms, the network statement alone does not guarantee neighbor formation. OSPF still needs active neighbor discovery on the link. If the interface is passive, the router advertises the connected network into OSPF but does not attempt to form an adjacency there.

This is a realistic routing troubleshooting pattern because the configuration can look mostly correct until you inspect the passive-interface setting.

Exam trap

A frequent exam trap is to incorrectly believe that OSPF process IDs must match between routers to exchange routes or that OSPF only works on serial links. Candidates may also overlook the passive-interface setting, assuming that the presence of correct network statements guarantees neighbor formation. The passive-interface command disables hello packets, which are essential for OSPF adjacency.

This subtle configuration detail often causes confusion because the router still advertises the network but refuses to form neighbors, leading to missing routes despite seemingly correct OSPF setup.

Why the other options are wrong

Incorrect because OSPF process IDs are locally significant and do not need to match between routers for adjacency or route exchange.

Incorrect because both routers' interfaces are in the same subnet 10.20.12.0/24, so subnet mismatch is not the cause of missing routes.

Incorrect because OSPF supports multiple link types including Ethernet; it is not limited to serial links only.

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126

Multi-Selectmedium

Which TWO statements correctly describe how a router selects the best path for a destination network when multiple routing table entries exist?

Select 2 answers

A.Routes with the longest prefix length (most specific) are preferred over routes with a shorter prefix.

B.If two routes have the same prefix length, the route with the higher administrative distance is selected.

C.When the administrative distance is identical, the router compares the metric and selects the route with the lowest metric.

D.A directly connected route has an administrative distance of 1, making it more trustworthy than any dynamic route.

E.Dynamic routes are always preferred over directly connected routes because they can adapt to network changes.

AnswersA, C

Routers perform a longest prefix match, meaning they compare the number of matching bits in the destination address with each route's subnet mask or prefix length. A more specific route, such as a /24 covering 192.168.1.0/24, is preferred over a less specific route like a /16 covering 192.168.0.0/16, because it identifies the destination network with greater precision. This rule is applied first, even before considering administrative distance or metric, because a longer match indicates a more exact route to the destination and, in classless routing, is always the most efficient forwarding decision.

Why this answer

Routers select the best path by first applying the longest prefix match rule (most specific subnet mask), so option A is correct. If two routes have the same prefix length, the router then compares administrative distance (AD) and prefers the lower AD; option B is incorrect because it says higher AD is selected. When AD is equal, the router uses metric and chooses the lowest metric, making option C correct.

Option D is false because directly connected routes have an AD of 0, not 1, and they are indeed more trustworthy than dynamic routes but not due to AD 1. Option E is wrong because directly connected routes are always preferred over dynamic routes regardless of adaptability.

Exam trap

Cisco often tests the exact administrative distance values (e.g., directly connected = 0, static = 1) and the correct comparison order (prefix length first, then AD, then metric) to catch candidates who confuse AD with metric or misremember default values.

Why the other options are wrong

The router selects the route with the lower administrative distance, not higher. Administrative distance is a measure of trustworthiness; a lower value indicates a more reliable source. For example, a static route (AD 1) is preferred over an OSPF route (AD 110).

Directly connected routes have an administrative distance of 0, not 1. An AD of 0 is the most trustworthy and cannot be overridden by any dynamic route. The value 1 is used for static routes.

Directly connected routes have an AD of 0, which is lower than any dynamic routing protocol (e.g., OSPF AD 110, EIGRP AD 90). Therefore, directly connected routes are always preferred over dynamic routes, not the other way around.

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127

MCQmedium

A router learns 203.0.113.0/24 through OSPF and 203.0.113.0/25 through a static route. Which route is used for traffic destined to 203.0.113.10?

A.The OSPF /24 route

B.The static /25 route

C.Both routes equally

D.Neither route because the prefixes overlap

AnswerB

The static /25 route is selected because forwarding decisions use longest-prefix match, not administrative distance. Even though OSPF has a higher administrative distance (110) compared to static's 1, that comparison applies only when two routes have identical prefix lengths. Since 203.0.113.0/25 is more specific than the /24 and also matches the destination address, the router installs and uses this route for all traffic within that /25 range. This is why the static /25 correctly wins.

Why this answer

Routers prefer the most specific matching route first. The /25 route is more specific than the /24 and includes 203.0.113.10.

Exam trap

Remember that the most specific route (longest prefix) is always preferred, regardless of the routing protocol.

Why the other options are wrong

The OSPF /24 route is less specific than the static /25 route. The longest prefix match rule dictates that the /25 route is preferred for destination 203.0.113.10, which falls within the /25 range.

Equal-cost load balancing only applies when multiple routes have the same prefix length and metric. Here, the prefix lengths differ (/24 vs /25), so the longest prefix match selects the /25 route exclusively.

Overlapping routes are common in routing tables and do not cause a problem. The router always selects the most specific match (longest prefix) for forwarding, so both routes can coexist.

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128

MCQhard

Refer to the exhibit. A network engineer is troubleshooting connectivity to server 10.10.10.130. The routing table contains both a static route and an OSPF route for overlapping prefixes. The engineer examines the specific routing entry for 10.10.10.130. Based on the output, why does the router choose the route via 10.1.1.2 instead of the OSPF route via 10.2.2.2 (for 10.10.10.0/24)?

A.The static route has a lower administrative distance (1) than the OSPF route (110).

B.The OSPF route is inactive because its next-hop 10.2.2.2 is down.

C.The static route has a longer prefix length (/26) than the OSPF route (/24), making it a more specific match.

D.The router prefers the static route because it has a metric of 0, which is better than the OSPF metric.

AnswerC

The deciding factor is longest prefix match, which is the first rule in IP route selection. The static route's mask of /26 matches 64 addresses, while the OSPF route's /24 matches 256 addresses; for any destination inside the /26, the static route is a longer, more specific match. Longest prefix match is evaluated before administrative distance or metric, so the /26 static route is preferred even though OSPF has a higher AD and a different metric.

Why this answer

The router selects the route via 10.1.1.2 because the static route has a prefix length of /26, which is longer (more specific) than the OSPF route's /24. When multiple routes to the same destination exist, the router uses the most specific match (longest prefix) regardless of administrative distance or metric. Since 10.10.10.130 falls within the 10.10.10.128/26 range, the /26 route is preferred over the /24 route.

Exam trap

Cisco often tests the longest prefix match rule by presenting overlapping routes with different administrative distances, leading candidates to incorrectly assume that lower AD always wins, when in fact prefix length is evaluated first.

Why the other options are wrong

This reflects a common misunderstanding that AD is the sole tie-breaker between routes from different sources, ignoring prefix length priority.

Candidates might assume that if the OSPF route is not used, it must be inactive; however, the exhibit does not show this.

Candidates may mistake metric for the primary selection criterion, not realizing prefix length dominates all other route comparison steps.

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129

MCQhard

A router has routes to 192.168.100.0/24 and 192.168.100.128/25. Which route is used for traffic to 192.168.100.140?

A.192.168.100.0/24

B.192.168.100.128/25

C.The default route

D.Neither route, because the prefixes overlap

AnswerB

This is correct because .140 falls within the 192.168.100.128/25 range.

Why this answer

The /25 route is used because it is the most specific matching prefix. In practical terms, 192.168.100.140 falls inside the upper half of the /24, which is exactly what the 192.168.100.128/25 route describes. Even though the /24 also matches, the router always prefers the narrower route when both are valid.

This is a direct longest-prefix-match question. It reinforces that specificity is checked before broader route-source preferences matter.

Exam trap

A frequent exam trap is assuming that the less specific route (192.168.100.0/24) will be used simply because it covers the entire subnet range or because it might have a better administrative distance. Candidates might also think overlapping prefixes cause routing conflicts that prevent either route from being used. However, Cisco routers resolve overlapping routes by always selecting the longest prefix match, which is the most specific subnet.

Ignoring this rule leads to incorrect answers and misunderstanding of routing behavior.

Why the other options are wrong

The 192.168.100.0/24 route is less specific than the 192.168.100.128/25 route. Although it matches the destination IP, the router prefers the more specific /25 route, so this option is incorrect.

The default route is only used when no more specific routes match the destination IP. Since both /24 and /25 routes match, the default route is not used, making this option incorrect.

Although the prefixes overlap, this is a normal and expected behavior in routing. The router resolves overlapping prefixes using longest prefix match, so traffic is forwarded correctly. Therefore, this option is incorrect.

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130

MCQhard

Based on the exhibit, why is the static route not being used for 172.18.9.10?

A.Because the connected /24 route is more specific than the static /16 route.

B.Because static routes are never used when a connected network exists anywhere in the table.

C.Because connected routes always have administrative distance 255.

D.Because static routes work only for default routing.

AnswerA

The router uses the longest-prefix match rule when selecting a route, so the /24 connected route is preferred over the /16 static route because it is more specific. The static /16 route remains in the routing table and will be used for other destinations in the 172.16.0.0/16 range that are not covered by the /24. Thus, the static route is not used for that particular subnet because of the /24's longer mask.

Why this answer

The static route is not being used because the connected route is the more specific match. In practical terms, route selection starts with prefix specificity. The static route covers a broad /16, but the destination 172.18.9.10 also falls inside a connected /24. The /24 wins because it is more specific.

This is a classic routing interpretation question because it tests whether you apply longest-prefix logic before thinking about route source preference.

Exam trap

A common exam trap is assuming that static routes are always preferred over connected routes or that connected routes have a higher administrative distance. Candidates might overlook the longest-prefix match rule and focus only on administrative distance or route type. This leads to the incorrect conclusion that the static /16 route should be used for 172.18.9.10, ignoring that the connected /24 route is more specific and therefore preferred.

Misunderstanding this concept causes errors in interpreting routing tables and route selection behavior.

Why the other options are wrong

This is incorrect because static routes are still used when no connected route matches the destination. The presence of any connected route does not prevent static routes from being used if they are more specific or the only match.

This is wrong because connected routes have an administrative distance of 0, not 255. The issue here is route specificity, not administrative distance values.

This is incorrect because static routes can be configured for any prefix length, not just default routes. They are valid for specific subnets and are commonly used for precise routing control.

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131

Multi-Selectmedium

Which three statements about IPv6 routing are correct? (Choose three.)

Select 3 answers

.IPv6 static routes can be configured using the 'ipv6 route' command.

.The next-hop address for a directly attached IPv6 static route can be a link-local address.

.OSPFv3 uses the same basic algorithm as OSPFv2 but is designed for IPv6.

.IPv6 routing is enabled by default on all Cisco routers.

.The default route in IPv6 is represented as ::/128.

.EIGRP for IPv6 uses the same autonomous system number as EIGRP for IPv4 and shares the same routing table.

Why this answer

All three statements are correct. The 'ipv6 route' command is used to configure static routes in IPv6, similar to 'ip route' in IPv4. A directly attached IPv6 static route can indeed use a link-local address as the next hop, which is common for point-to-point interfaces.

OSPFv3 (OSPF for IPv6) uses the same fundamental SPF algorithm and link-state concepts as OSPFv2 but is designed to support IPv6 addressing and runs per-link rather than per-subnet.

Exam trap

Cisco often tests the nuance that a link-local address can be used as a next hop for a directly attached IPv6 static route only if the exit interface is explicitly specified, leading candidates to incorrectly think link-local addresses are never valid next hops.

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132

MCQhard

Why is R1 not installing the floating static default route into the routing table?

A.Because the OSPF default route has a lower administrative distance than the floating static route.

B.Because static default routes can never be used when OSPF is enabled.

C.Because the static default route must use a /24 mask instead of 0.0.0.0.

D.Because the next hop of a floating route must be a loopback address.

AnswerA

The OSPF default route has an AD of 110, while a floating static route is intentionally configured with a higher AD, such as 200. Because the router prefers lower AD, OSPF's default is installed in the routing table. The floating static route remains in the configuration as a backup and only becomes active if OSPF fails or the OSPF default disappears.

Why this answer

The floating static default route is not installed because the primary default route is already present and has a lower administrative distance. In practical terms, a floating static route is meant to sit in reserve and appear only when the preferred route is unavailable. Since the OSPF default route is active and has a better administrative distance, the backup route is not used yet.

This is a classic route-preference question. The key idea is not just that a static route exists, but that a higher-distance static route is intentionally designed to lose until the primary path disappears.

Exam trap

A frequent exam trap is assuming that a static default route must always appear in the routing table regardless of other routes. Candidates often think the floating static route is missing or misconfigured when it is simply suppressed due to its higher administrative distance compared to the OSPF default route. This misunderstanding leads to incorrect troubleshooting steps or answer choices.

Remember, floating static routes are designed to be backup routes and only become active when the primary route is unavailable, so their absence in the routing table under normal conditions is expected behavior.

Why the other options are wrong

Incorrect. Static default routes can coexist with OSPF routes. The router uses administrative distance to determine which route to install, so static routes are not automatically ignored when OSPF is enabled.

Incorrect. A default route must use the destination 0.0.0.0 with a mask of 0.0.0.0. Using a /24 mask is invalid for a default route and would not solve the issue of route selection.

Incorrect. Floating static routes do not require the next hop to be a loopback address. The next hop can be any reachable IP address, so this is not the reason the route is not installed.

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133

Drag & Drophard

Drag and drop the following steps into the correct order for the router's routing table lookup process when forwarding a packet to a destination IP address, including the best-path selection logic.

Drag steps to the numbered slots on the right, or tap a step then tap a slot.

Steps

Order

1Step 1

2Step 2

3Step 3

4Step 4

Why this order

The routing table lookup first matches the destination with the longest prefix, then applies tie-breakers: lowest administrative distance, then lowest metric, to determine the best path for forwarding.

Exam trap

Do not confuse the order of tie-breakers: administrative distance is always considered before metric. Also, remember that routing table lookup uses longest prefix match, not first match like ACLs.

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134

Multi-Selectmedium

Which two statements accurately describe OSPF route selection or behavior at the CCNA level?

Select 2 answers

A.OSPF uses cost as its metric for choosing paths within OSPF.

B.OSPF compares its metric directly against EIGRP metrics across protocols.

C.OSPF route preference versus other route sources involves administrative distance.

D.OSPF process IDs must match between all neighboring routers.

E.OSPF can never install equal-cost paths.

AnswersA, C

This is correct because cost is the standard OSPF metric.

Why this answer

OSPF uses cost as its metric for path selection within the protocol, and OSPF routes are compared against other route sources using administrative distance when cross-protocol decisions are needed. OSPF supports equal-cost multi-path (ECMP), meaning it can install multiple equal-cost paths to the same destination, so option E is incorrect. The wrong answers confuse cost with administrative distance, treat process IDs as globally significant, or incorrectly direct cross-protocol metric comparisons.

Exam trap

A frequent exam trap is confusing OSPF’s cost metric with administrative distance or thinking that OSPF process IDs must match between neighbors. Many candidates incorrectly believe that OSPF compares its metric directly against EIGRP metrics or that process IDs are globally significant. This misunderstanding leads to wrong answers because OSPF cost is only used internally within OSPF to select the best path, while administrative distance is used to compare routes from different protocols.

Also, OSPF process IDs are locally significant identifiers and do not need to match for adjacency to form.

Why the other options are wrong

Option B is incorrect because OSPF does not compare its metric directly against EIGRP metrics. Metrics are protocol-specific and only administrative distance is used to compare routes across different protocols.

Option D is incorrect because OSPF process IDs are locally significant and do not need to match between neighboring routers. Adjacency forms based on matching parameters like area ID and authentication, not process ID.

Option E is incorrect because OSPF supports equal-cost multipath (ECMP) routing, allowing multiple routes with the same cost to be installed and used simultaneously for load balancing.

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135

Drag & Dropmedium

Drag and drop the following OSPFv2 neighbor state transitions into the correct order, starting from the initial Down state on a broadcast or point-to-point network (non-NBMA).

Drag steps to the numbered slots on the right, or tap a step then tap a slot.

Steps

Order

1Step 1

2Step 2

3Step 3

4Step 4

Why this order

The standard OSPF neighbor state machine on broadcast and point-to-point networks proceeds: Down, Init, 2-Way, ExStart, Exchange, Loading, Full. The Attempt state exists only on NBMA networks and is not used here. Option D correctly lists the first five states in order: Down → Init → 2-Way → ExStart → Exchange.

Other options incorrectly include the NBMA-only Attempt state or misorder the states like Loading before Exchange.

Exam trap

Do not confuse the standard OSPF neighbor states with the NBMA-specific Attempt state; unless the network type is explicitly NBMA, assume the common broadcast/point-to-point order omitting Attempt.

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136

MCQhard

A network engineer configures a primary default route via Gi0/0 (next-hop 192.168.12.2) and a floating static default route via Gi0/1 (next-hop 192.168.12.6) with AD 200. To test failover, the engineer issues the shutdown command on Gi0/0. After this, the router does not have a default route in the routing table. Which problem explains this behavior?

A.The backup interface Gi0/1 is administratively down, making the next-hop unreachable.

B.The floating static route uses an administrative distance of 200, which is too low to replace the primary route.

C.The primary default route remains in the routing table because shutting down Gi0/0 does not remove the static route.

D.The floating static route is missing a track object, so the router cannot detect the primary path failure.

AnswerA

With Gi0/1 administratively shut down, its interface state is down at both Layer 1 and Layer 2, so the router cannot use it as a valid output interface. A static route whose configured next-hop resides on a down interface is considered unreachable, and the router will not install it in the routing table. Because both Gi0/0 and Gi0/1 are unavailable, no default route is present, and the router has no path to the unknown destination.

Why this answer

A floating static route is installed only if its next-hop is reachable and the primary route (with lower AD) is absent. Shutting down Gi0/0 removes the primary route. However, backup interface Gi0/1 is also administratively down, so the next-hop 192.168.12.6 is unreachable, and the floating route is not installed.

Option A correctly identifies the interface status as the root cause. Option B is wrong because a higher AD (200) correctly designates this as a backup; a lower AD would make it primary. Option C is false; shutting down an interface removes connected routes, which causes the recursive static route to be purged.

Option D is incorrect because floating static routes do not require a track object—the AD difference alone dictates failover when the primary is removed.

Exam trap

The most common mistake is assuming a floating static route will automatically be installed when the primary route disappears, forgetting that the next-hop must be reachable.

Why the other options are wrong

A lower AD would make it preferred, defeating the purpose of a floating route.

The primary route is removed from the table when the interface goes down.

Track objects are optional enhancements for faster failover but not mandatory for floating static operation.

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137

Drag & Dropmedium

Drag and drop the following steps into the correct order to configure and verify OSPFv3 neighbor adjacency using link-local addresses in area 0.

Drag steps to the numbered slots on the right, or tap a step then tap a slot.

Steps

Order

1Step 1

2Step 2

3Step 3

4Step 4

5Step 5

Why this order

The correct order enables IPv6 unicast routing globally, creates the OSPFv3 process, enters interface configuration, assigns the interface to the OSPFv3 process in area 0 (which activates OSPFv3 on the link), and finally verifies the neighbor relationship. IPv6 unicast routing must be enabled first because OSPFv3 requires IPv6 packet forwarding. The router process must exist before an interface can be associated with it.

Assigning the interface to area 0 triggers Hello packet exchange over link-local addresses. The show command confirms the adjacency formed.

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138

MCQeasy

Which static route on R1 sends all unknown IPv4 destinations to next-hop address 192.0.2.1?

A.ip route 0.0.0.0 255.255.255.255 192.0.2.1

B.ip route 0.0.0.0 0.0.0.0 192.0.2.1

C.ip route 255.255.255.255 0.0.0.0 192.0.2.1

D.ip default-gateway 192.0.2.1

AnswerB

The command ip route 0.0.0.0 0.0.0.0 192.0.2.1 installs a default static route whose prefix and mask are both all zeros. Because the routing table uses longest-prefix-match, this quad-zero route matches every IPv4 destination that is not matched by a more specific route. R1 will therefore forward all unknown IPv4 traffic out the interface toward next-hop 192.0.2.1.

Why this answer

A quad-zero route is the IPv4 default route. It matches destinations that do not have a more specific entry in the routing table.

Exam trap

A frequent exam trap is selecting a static route with the destination 0.0.0.0 but an incorrect subnet mask like 255.255.255.255, which matches only the single host 0.0.0.0 rather than all unknown destinations. Another common mistake is confusing the 'ip default-gateway' command with a default route; the former is used only on devices that do not perform routing, such as Layer 2 switches, and does not influence routing decisions on routers. Candidates must recognize that the default route requires both destination and mask to be 0.0.0.0 to function correctly as a catch-all route for unknown IPv4 destinations.

Why the other options are wrong

The route 'ip route 0.0.0.0 255.255.255.255 192.0.2.1' incorrectly uses a subnet mask of 255.255.255.255, which matches only the single host 0.0.0.0, not all unknown destinations. Therefore, it does not serve as a default route.

The route 'ip route 255.255.255.255 0.0.0.0 192.0.2.1' reverses the destination and mask fields, creating an invalid route that does not function as a default route or any valid static route.

'ip default-gateway 192.0.2.1' sets the default gateway for devices that do not perform routing, such as Layer 2 switches. It does not create a routing entry on routers and therefore cannot be used to send unknown IPv4 destinations.

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139

Drag & Dropmedium

Drag and drop the following steps into the correct order to configure and verify HSRP with priority and preemption on an interface.

Drag steps to the numbered slots on the right, or tap a step then tap a slot.

Steps

Order

1Step 1

2Step 2

3Step 3

4Step 4

5Step 5

6Step 6

Why this order

First, enter interface configuration mode to start configuring the specific interface. Next, assign an IP address because HSRP requires a real IP on the interface for communication between HSRP routers. After that, define the HSRP group and virtual IP, which clients use as their default gateway.

Then set a higher priority to influence the active router election; priority must be configured before enabling preemption, as preemption relies on priority to determine when to take over. Finally, exit configuration mode and verify with show standby to confirm the HSRP state.

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140

MCQhard

A router has routes to 192.168.0.0/16 and 192.168.50.0/24. Which route is used for traffic to 192.168.50.99?

A.192.168.0.0/16

B.192.168.50.0/24

C.The default route

D.Both routes equally

AnswerB

This is correct because it is the more specific route for the destination.

Why this answer

The 192.168.50.0/24 route is used because it is more specific. In practical terms, even though the /16 also matches, the router always prefers the route that describes the destination more narrowly. Since 192.168.50.99 falls inside the /24, longest-prefix match chooses that entry.

This is a basic but essential routing rule. The broader /16 still matters for other destinations in 192.168.0.0/16, but not for this one.

Exam trap

Remember that routers prefer the most specific route, not the broadest. Always look for the longest prefix match.

Why the other options are wrong

The route 192.168.0.0/16 is less specific (larger subnet) than the matching /24 route. In longest prefix match routing, the more specific route (192.168.50.0/24) is always preferred for the destination 192.168.50.99.

A default route (0.0.0.0/0) is only used when no more specific route matches the destination. Since both 192.168.0.0/16 and 192.168.50.0/24 match 192.168.50.99, the default route is not considered.

Routers do not load balance between routes of different prefix lengths for the same destination. The longest prefix match rule selects a single best route. Both routes are not used equally; the /24 route is chosen.

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141

MCQhard

Refer to the exhibit. A network administrator is troubleshooting why not all OSPF neighbors are fully adjacent on a multi-access broadcast segment. After issuing the show ip ospf neighbor command on R1, the output is displayed. What is the most likely cause of the 2WAY/DROTHER state for neighbor 172.16.1.1?

A.The neighbor is a DROther and a full adjacency with another DROther is not required; adjacency is formed only with the DR and BDR.

B.The OSPF hello and dead timers are mismatched between R1 and neighbor 172.16.1.1.

C.The network type is configured as point-to-point on one side and broadcast on the other, causing a DR/BDR election failure.

D.The neighbor's router ID 172.16.1.1 is not reachable, preventing the completion of the adjacency process.

AnswerA

The exhibit shows neighbor 172.16.1.1 in state 2WAY/DROTHER. In a broadcast multi-access OSPF network, DROthers exchange hellos and reach 2-Way state with each other but stop at that stage, establishing full adjacency only with the DR and BDR. This is standard OSPF behavior and the most likely reason for the state.

Why this answer

In a multi-access broadcast OSPF network, only the Designated Router (DR) and Backup Designated Router (BDR) form full adjacencies with all other routers. DROthers (routers that are neither DR nor BDR) only form full adjacencies with the DR and BDR, and remain in the 2WAY state with other DROthers. The show ip ospf neighbor output on R1 shows neighbor 172.16.1.1 as 2WAY/DROTHER, which is normal behavior because both are DROthers and do not need to exchange LSAs directly.

Exam trap

Cisco often tests the misconception that any neighbor state other than FULL is a problem, but here the trap is that 2WAY/DROTHER is actually expected behavior for non-DR/BDR routers on a broadcast segment, and candidates may incorrectly assume a timer mismatch or reachability issue.

Why the other options are wrong

Candidates mistakenly think any non-FULL state implies a timer mismatch, overlooking that timer issues prevent even reaching 2WAY.

Some candidates assume any DR/BDR-related issue indicates a network type mismatch, but the exhibit clearly shows successful DR/BDR formation, ruling out this option.

Candidates may confuse LSA reachability with neighbor adjacency requirements. The 2WAY state proves basic connectivity is intact.

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142

MCQhard

A network engineer configures a static route: ip route 192.168.10.0 255.255.255.0 10.1.1.2. The next hop 10.1.1.2 is reachable via OSPF. Later, the engineer notices that the route to 192.168.10.0/24 has disappeared from the routing table. What is the most likely cause?

A.The OSPF route to 10.1.1.0/30 has been lost, making the next-hop address 10.1.1.2 unresolvable.

B.The static route has a higher administrative distance than OSPF, so OSPF's route to 192.168.10.0/24 replaced it.

C.The static route uses a next-hop IP address that is not directly connected, which is unsupported on this platform.

D.A routing loop caused by recursive lookups has suppressed the static route to prevent loops.

AnswerA

A recursive static route requires a next-hop that is resolvable via an existing route. Without the OSPF route to the subnet containing 10.1.1.2, the router cannot reach the next hop and removes the static route from the routing table.

Why this answer

The static route to 192.168.10.0/24 uses 10.1.1.2 as the next-hop address. For a static route with a next-hop IP (rather than an exit interface) to be installed in the routing table, the next-hop must be reachable via a valid route in the routing table. If the OSPF route to the subnet containing 10.1.1.2 (e.g., 10.1.1.0/30) is lost, the next-hop becomes unreachable, and the static route is removed from the routing table.

This is the most likely cause of the route disappearing.

Exam trap

Cisco often tests the concept that a static route with a next-hop IP requires a valid route to that IP in the routing table, and candidates mistakenly think the static route will always remain or that administrative distance is the cause of its removal.

Why the other options are wrong

Believing that a static route is removed from the routing table when a better route exists, rather than understanding it remains but is inactive.

Assuming that a static route's next-hop must be directly attached, ignoring that recursive routing via another routing protocol or static route is allowed.

Thinking that recursive static routes are prone to loop suppression, rather than understanding that the route is simply withdrawn when the next-hop is no longer reachable.

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143

MCQmedium

A router advertises its LAN network into OSPF, but no OSPF Hellos should be sent toward end-user devices on that LAN. Which configuration approach solves this cleanly?

A.Use ip ospf cost 65535 on the LAN interface

B.Configure the LAN interface as a passive interface in OSPF

C.Disable OSPF globally and redistribute connected routes

D.Convert the LAN interface to a loopback

AnswerB

The `passive-interface` command under the OSPF process tells OSPF to stop transmitting Hello packets on that interface while still injecting the interface's subnet as an OSPF route. This preserves full route reachability into the LAN without forming neighbor adjacencies, cutting unnecessary protocol overhead. It is the standard, purpose-built mechanism for LAN-facing OSPF interfaces.

Why this answer

A passive interface advertises the connected subnet into OSPF without sending or processing Hellos on that interface. That is exactly what you want for user-facing LANs with no OSPF neighbors.

Exam trap

A frequent exam trap is selecting the option to increase the OSPF cost on the LAN interface to prevent Hello packets. While adjusting the cost changes the metric used for route selection, it does not stop the router from sending or receiving OSPF Hellos. Another common mistake is to disable OSPF globally and redistribute connected routes, which is unnecessarily complex and does not address the problem of suppressing Hellos on a specific interface.

Additionally, converting the LAN interface to a loopback is irrelevant because loopbacks are logical interfaces used for router IDs and testing, not for controlling OSPF Hello behavior on physical LAN interfaces.

Why the other options are wrong

Using 'ip ospf cost 65535' on the LAN interface only changes the OSPF metric for that interface. It does not prevent the router from sending or receiving OSPF Hello packets, so neighbor adjacencies can still form, which is not the desired behavior.

Disabling OSPF globally and redistributing connected routes is an overly complex and unnecessary approach. It does not selectively stop Hello packets on the LAN interface and can introduce routing complexity and instability.

Converting the LAN interface to a loopback interface changes the interface type entirely and is not a standard or practical solution for suppressing OSPF Hellos on a LAN. Loopbacks are logical interfaces used for router IDs and testing, not for controlling OSPF Hello behavior.

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144

Matchingmedium

Match each route source or route type to its most accurate description.

Drag a concept onto its matching description — or click a concept then click the description.

Concepts

Matches

Present because the network is directly attached

Manually configured route

Learned dynamically through the routing protocol

Backup static route with higher administrative distance

Why these pairings

Connected routes are automatically installed when an interface is configured with an IP address and is in the up/up state. Static routes are manually configured by an administrator to specify a fixed path. OSPF is a link-state routing protocol that uses cost as its metric and maintains a complete topology database.

EIGRP is a hybrid protocol that uses bandwidth and delay as metrics and supports unequal-cost load balancing.

Exam trap

The exam often tests the automatic nature of connected routes. Do not confuse them with static or dynamic routes. Remember that connected routes appear only when the interface is up/up.

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145

MCQmedium

Which OSPF network type on Ethernet performs a DR and BDR election by default?

A.Point-to-point

B.Broadcast

C.Point-to-multipoint nonbroadcast

D.Loopback

AnswerB

On Ethernet segments, OSPF automatically defaults to the broadcast network type. This type relies on multicast hello packets to 224.0.0.5 and elects a Designated Router (DR) and Backup Designated Router (BDR) to minimize the number of adjacencies and reduce LSA flooding on the multi-access link. Therefore, broadcast is the correct network type where DR/BDR election occurs.

Why this answer

Broadcast multiaccess networks such as Ethernet elect a DR and BDR by default.

Exam trap

A frequent exam trap is selecting point-to-point or point-to-multipoint nonbroadcast as the network type that performs DR/BDR elections. Candidates often assume any multi-router link requires DR/BDR, but OSPF only elects DR/BDR on broadcast and NBMA networks. Point-to-point links connect exactly two routers and do not need DR/BDR, while point-to-multipoint nonbroadcast requires manual neighbor configuration and does not elect DR/BDR by default.

Misunderstanding these distinctions leads to incorrect answers. Remember, Ethernet interfaces default to broadcast network type, which triggers DR/BDR elections automatically.

Why the other options are wrong

Point-to-point links connect only two routers directly and do not require or perform DR/BDR elections because there is no need to reduce flooding on a single link. Selecting this option is incorrect for Ethernet interfaces that default to broadcast.

Point-to-multipoint nonbroadcast network type requires manual neighbor configuration and does not perform DR/BDR elections by default. This does not match the default behavior of Ethernet interfaces.

Loopback interfaces are virtual interfaces used for router identification and do not participate in OSPF DR/BDR elections because they are not multiaccess networks.

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146

MCQmedium

Why is a default route useful on a small branch router connected to a single upstream provider?

A.It provides a simple next hop for unknown destinations toward the upstream connection.

B.It makes every route more specific.

C.It replaces the need for any interface addressing.

D.It forces all users into one VLAN.

AnswerA

The default route is a catch-all route, typically 0.0.0.0/0 for IPv4, that matches any destination not found in the routing table. On a small branch router, it points to the upstream ISP or WAN gateway, allowing all unknown traffic to be forwarded toward the provider with a single simple next hop. This eliminates the need to manually configure many remote network routes.

Why this answer

A default route is useful because it gives the branch a simple fallback next hop for destinations the router does not know specifically. In practical terms, the branch router does not need a full table of every external destination if all unknown traffic should go upstream. That keeps the design simple and efficient.

This is one of the most practical default-route use cases in small or edge networks.

Exam trap

A frequent exam trap is assuming that a default route makes every route more specific or that it replaces the need for interface addressing. Some candidates mistakenly believe the default route refines routing granularity, but it actually represents the least specific route, catching all unknown destinations. Others incorrectly think default routes eliminate the need for IP addresses on interfaces, which is false because interfaces must always have valid IP configurations for routing to function.

Misunderstanding these points can lead to incorrect answers about routing behavior and network design.

Why the other options are wrong

Incorrect because a default route is the least specific route and does not make routes more specific; it serves as a catch-all for unknown destinations.

Incorrect because interface addressing is mandatory for routing to function properly; a default route does not replace the need for IP addresses on interfaces.

Incorrect because default routes influence packet forwarding decisions and have no impact on VLAN assignments, which are Layer 2 configurations.

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147

PBQmedium

You are connected to R1 via the console. R1 and R2 are configured with EIGRP AS 100. R1 has two paths to the 172.16.1.0/24 network: one via a FastEthernet link to R2 (bandwidth 100 Mbps, delay 100 microseconds) and another via a serial link to R2 (bandwidth 1.544 Mbps, delay 20000 microseconds). The EIGRP metric is calculated using the default K-values. The FastEthernet link is preferred, but you need to make the serial link the backup by adjusting the administrative distance.

Network Topology

Hints

•The default administrative distance for EIGRP is 90 for internal routes.
•Use an administrative distance value greater than 90 to make the static route less preferred.
•The command uses 'ip route' with an AD value at the end.

A.Configure a static route to 172.16.1.0/24 with next-hop 10.0.0.6 and administrative distance 170.

B.Configure a static route to 172.16.1.0/24 with next-hop 10.0.0.6 and administrative distance 90.

C.Configure a static route to 172.16.1.0/24 with next-hop 10.0.0.6 and administrative distance 1.

D.Configure a static route to 172.16.1.0/24 with next-hop 10.0.0.6 and administrative distance 255.

AnswerA

solution

! R1
ip route 172.16.1.0 255.255.255.0 10.0.0.6 170

Why this answer

A floating static route is configured with an administrative distance of 170, which is higher than EIGRP's default distance of 90. This ensures that the static route is only used when the EIGRP route is not available. The static route points to the next-hop IP address of R2's serial interface.

Exam trap

Remember that a floating static route must have an administrative distance higher than the dynamic protocol's AD. EIGRP's default AD is 90, so choose an AD like 170. Avoid using AD 255, as it means the route is not installed.

Why the other options are wrong

The specific factual error is that an AD of 90 does not make the static route less preferred than EIGRP; it creates equal preference.

The specific factual error is that a lower AD makes the route more preferred, so the static route would override EIGRP.

The specific factual error is that AD 255 means the route is not trusted and is effectively ignored.

148

MCQhard

A router has an OSPF-learned route to a destination prefix and also a directly connected route to a broader supernet that includes that destination. The OSPF route is more specific. Which route is used for the destination?

A.The more specific OSPF route

B.The directly connected broader route

C.Both routes equally

D.Neither route can be used because the sources differ

AnswerA

This is correct because the most specific matching prefix is preferred first.

Why this answer

The more specific OSPF route is used. In practical terms, route specificity is checked before broader route-source considerations when the prefixes are different. Even though the connected route is a directly attached source and often strongly trusted, it still loses if it is less specific than another matching route.

This is a subtle route-selection question because it combines source type and specificity. The key is that longest-prefix match comes first.

Exam trap

A common exam trap is assuming that directly connected routes always take precedence over OSPF routes because they have a lower administrative distance. Candidates may incorrectly select the broader directly connected route, forgetting that routers first apply longest prefix match before considering administrative distance. This leads to the mistaken belief that a less specific connected route overrides a more specific OSPF route.

The trap is confusing route source preference with prefix specificity, which can cause incorrect answers on routing questions involving multiple route sources.

Why the other options are wrong

This option is incorrect because a directly connected route, even though it has a lower administrative distance, does not override a more specific OSPF route due to prefix length precedence.

This option is incorrect because routers do not use multiple routes equally when one route is a more specific match; only the best matching route is used for forwarding.

This option is incorrect because routers can compare and select routes from different sources; differing sources do not prevent route usage if one route is the best match.

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149

MCQmedium

Why is a default route often described as a route of last resort?

A.Because it is used only when no more specific route matches.

B.Because it always has the lowest bandwidth.

C.Because it is more specific than any other route.

D.Because it can be learned only through OSPF.

AnswerA

The default route, 0.0.0.0/0, matches every IP destination, but routers use longest-prefix-match forwarding. A packet is sent via the default route only when no other route in the routing table has a longer prefix length that matches the destination. Thus it acts as the final fallback, or route of last resort.

Why this answer

It is described that way because it is used only when no more specific route matches the destination. In practical terms, the router checks for connected, static, or dynamic routes that describe the destination more precisely. If it finds none, the default route becomes the fallback path.

This phrase captures the default route’s purpose exactly. It is not the fastest route or the most specific route. It is simply the catch-all route for otherwise unknown destinations.

Exam trap

A frequent exam trap is assuming the default route is the most specific or fastest route, or that it is exclusively learned through OSPF. Candidates may confuse the default route with routes learned dynamically or with specific metrics. The default route is actually the least specific route, matching all destinations not covered by other entries.

Misunderstanding this can lead to incorrect answers about routing behavior and protocol dependencies, especially since default routes can be configured statically or learned via multiple protocols, not just OSPF.

Why the other options are wrong

This option is incorrect because bandwidth does not determine whether a route is a default route. Default routes are about specificity and fallback behavior, not link speed or bandwidth.

This option is incorrect because the default route is the least specific route, not more specific than others. It matches all destinations not covered by other routes, so it cannot be more specific.

This option is incorrect because default routes can be learned through various routing protocols such as OSPF, EIGRP, or configured statically. It is not exclusive to OSPF.

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150

PBQhard

You have console access to both R1 and R2. Configure OSPFv2 on both routers to establish a single-area adjacency in area 0. The link between R1 and R2 uses 10.0.0.0/30. Currently, OSPF is not configured on either router. After configuration, verify the adjacency forms and routes are exchanged.

Network Topology

Hints

•Use 'router ospf <process-id>' to enter OSPF configuration mode.
•The network statement uses a wildcard mask, not a subnet mask. For a /30, use 0.0.0.3.
•Remember to set a router-id; it can be any IP address, but must be unique per router.

A.Configure 'router ospf 1' on R1 and R2, set router-id, and use 'network 10.0.0.0 0.0.0.3 area 0' on both routers.

B.Configure 'router ospf 1' on R1 only, and use 'network 10.0.0.0 0.0.0.3 area 0' on R1; R2 does not need OSPF configuration because it will learn routes via the directly connected interface.

C.Configure 'router ospf 1' on both routers, set router-id, and use 'network 10.0.0.0 255.255.255.252 area 0' on both routers.

D.Configure 'router ospf 1' on both routers, set router-id, and use 'network 10.0.0.0 0.0.0.0 area 0' on both routers.

AnswerA

solution

! R1
configure terminal
router ospf 1
router-id 1.1.1.1
network 10.0.0.0 0.0.0.3 area 0
network 192.168.1.0 0.0.0.255 area 0
network 10.1.1.1 0.0.0.0 area 0
passive-interface GigabitEthernet0/1
passive-interface Loopback0
end

Why this answer

The essential requirement is enabling OSPFv2 on both routers with matching area 0 on the 10.0.0.0/30 link. On R1 and R2, enter 'router ospf 1', set a unique router-id, and use 'network 10.0.0.0 0.0.0.3 area 0' to advertise the link. The solution commands include optional networks (192.168.1.0/24 and Loopback0) that are not required for the adjacency and are shown only as examples; candidates should focus on the link network.

After configuration, 'show ip ospf neighbor' should show a FULL state. Common mistakes include using a subnet mask instead of a wildcard mask (option C) or a /32 wildcard (option D), and not configuring OSPF on R2 (option B).

Exam trap

Remember that OSPF network statements use wildcard masks, not subnet masks. Also, both routers must be configured; OSPF does not automatically enable on all interfaces. Use 'show ip ospf neighbor' to verify adjacency formation.

Why the other options are wrong

The specific factual error is that OSPF is a dynamic routing protocol that must be enabled on both ends of a link for adjacency to form; one-sided configuration does not work.

The specific factual error is confusing subnet masks with wildcard masks; OSPF uses inverse masks in network statements.

The specific factual error is using a host wildcard mask that does not cover the actual interface IPs; the correct wildcard mask must include the range of IPs on the link.

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