CCNA IP Routing Questions — Page 4 of 4

226

MCQhard

A router has a static route and a RIP route for the same destination prefix. What is the primary reason the static route is preferred over the RIP route?

A.Because the static route has a lower administrative distance for the same prefix.

B.Because RIP can never be installed when static routing is configured anywhere.

C.Because RIP is valid only for host routes.

D.Because static routes are always more specific than RIP routes.

AnswerA

Both the static and RIP routes share the same /16 prefix, so the longest-match rule cannot differentiate them. In that case, Cisco IOS compares administrative distance values: static routes default to AD 1, while RIP defaults to AD 120. Since a lower AD is always preferred, the static route is installed in the routing table and used for forwarding. That is the strongest reason because the prefixes are identical, making AD the decisive tie-breaker.

Why this answer

The static route is preferred because both routes describe the same destination prefix and the static route has the lower administrative distance. In practical terms, longest-prefix match does not break the tie because the prefixes are equal. The router then compares source trust, and static routing wins over RIP by default.

This is a core route-selection concept and a very exam-relevant comparison.

Exam trap

Do not confuse administrative distance with metrics or prefix length; administrative distance is the deciding factor here.

Why the other options are wrong

This option is incorrect because RIP can coexist with static routes in a routing table; static routes do not prevent RIP routes from being installed. Both routing protocols can be used simultaneously, and the routing decision is based on administrative distance.

This option is wrong because static routes are not inherently more specific than RIP routes; both can have varying levels of specificity depending on the configuration. The preference of static routes over RIP is determined by administrative distance, not specificity.

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227

PBQhard

You are connected to R1, a multilayer switch acting as an HSRP active gateway for VLAN 100. The network requires R1 to be the active router with a virtual IP of 192.168.100.1. Currently, both R1 and the peer router R2 show as active in 'show standby brief', and the virtual IP is misconfigured. Configure HSRP on R1 to fix these issues: set priority to 110, enable preempt, correct the virtual IP, and track interface GigabitEthernet0/1 (decrement priority by 20 if it goes down).

Network Topology

Hints

•Check the virtual IP address configured under the standby group — it should match the expected virtual IP.
•Preempt is disabled by default; verify if it's configured to allow R1 to become active after a failure.
•Use 'show standby' to see all details including tracking status.

A.interface Vlan100 standby 100 ip 192.168.100.1 standby 100 priority 110 standby 100 preempt standby 100 track GigabitEthernet0/1 20

B.interface Vlan100 standby 100 ip 192.168.100.254 standby 100 priority 110 standby 100 preempt standby 100 track GigabitEthernet0/1 20

C.interface Vlan100 standby 100 ip 192.168.100.1 standby 100 priority 100 standby 100 preempt standby 100 track GigabitEthernet0/1 20

D.interface Vlan100 standby 100 ip 192.168.100.1 standby 100 priority 110 standby 100 track GigabitEthernet0/1 20

AnswerA

solution

! R1
interface Vlan100
standby 100 ip 192.168.100.1
standby 100 priority 110
standby 100 preempt
standby 100 track GigabitEthernet0/1 20

Why this answer

The problem had multiple issues: the virtual IP was wrong (192.168.100.254 instead of 192.168.100.1), preempt was not enabled (both routers could claim active), and priority was default (100). Additionally, interface tracking was missing to decrement priority if the upstream link failed. The solution consists of four commands: 'standby 100 ip 192.168.100.1' to set the correct virtual IP, 'standby 100 priority 110' to make R1 the active router, 'standby 100 preempt' to allow R1 to reclaim active role after recovery, and 'standby 100 track GigabitEthernet0/1 20' to reduce priority by 20 if that interface goes down.

Exam trap

Watch out for three common HSRP pitfalls: (1) virtual IP must match the configured gateway, (2) preempt is required for a router to reclaim active role after recovery, and (3) priority must be higher than the peer to be preferred. Also, remember that interface tracking decrements priority, so the tracked interface must be specified correctly.

Why the other options are wrong

The virtual IP address is wrong; it should be 192.168.100.1, not 192.168.100.254.

Priority must be higher than the default (100) to ensure R1 becomes the active router; 110 is required.

Preempt is required to allow R1 to reclaim the active role when its priority becomes higher again after a failure.

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228

MCQhard

After configuring a static discard route with the command 'ip route 0.0.0.0 0.0.0.0 Null0 254' on R1, a network engineer finds that traffic to destinations that are not in the routing table is still being forwarded out to the ISP instead of being dropped. What is the most likely cause?

A.The Null0 interface is administratively shut down.

B.The address 0.0.0.0/0 is an invalid destination for a static route because it is not a real network.

C.The static discard route must include a next-hop IP address instead of specifying Null0 as the interface.

D.The ISP static default route has an administrative distance of 1, which is lower than the administrative distance of 254 set for the Null0 route.

AnswerD

When a router has multiple routes for the same 0.0.0.0/0 prefix, it selects the one with the lowest administrative distance. The ISP route with AD 1 wins, so traffic never matches the AD 254 Null0 discard route.

Why this answer

The static discard route with an administrative distance of 254 is less preferred than the ISP default route with an administrative distance of 1. Since the ISP route has a lower AD, it remains in the routing table and is used for forwarding traffic to unknown destinations, overriding the discard route. The Null0 route only becomes active if the ISP route is removed or fails, as the router always selects the route with the lowest administrative distance.

Exam trap

Cisco often tests the concept that administrative distance determines route preference, and the trap here is that candidates assume a static route to Null0 will always be used for discarding traffic, forgetting that a lower-AD route (like the ISP default) will take precedence.

Why the other options are wrong

Candidates often assume that a route pointing to an interface requires that interface to be up, but Null0 is always available.

A misconception that the default route is special and cannot be used with Null0, but any valid IP prefix can be directed to Null0 to create a discard route.

Confusing Null0 routes with Ethernet interface routes, which require a next hop, leads to the incorrect belief that a next hop is mandatory for all static routes.

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229

PBQhard

You are troubleshooting a network connectivity issue on R1. The network 192.168.10.0/24 behind R2 must be reachable from R1 via the primary path through R2 (192.0.2.2). A backup path via R3 (198.51.100.2) should automatically take over if the primary fails. Currently, traffic to 192.168.10.0/24 is incorrectly using the backup path even though the primary path is operational. Analyze the routing table and configuration, then fix the issue so that the primary path is preferred when available.

Network Topology

Hints

•Compare the Administrative Distance values in the routing table for the two paths.
•The default AD for a static route is 1; a floating static uses a higher AD.
•You need to swap the AD values between the primary and backup routes.

A.Remove the static route to 192.168.10.0/24 via 198.51.100.2 and add a floating static route via 198.51.100.2 with AD 200. Ensure the primary route via 192.0.2.2 uses default AD 1.

B.Change the AD of the static route via 192.0.2.2 to 200 and the AD of the route via 198.51.100.2 to 1.

C.Add a static route to 192.168.10.0/24 via 192.0.2.2 with AD 1 and remove the existing route via 198.51.100.2.

D.Configure a policy-based route to prefer the next-hop 192.0.2.2 for traffic to 192.168.10.0/24.

AnswerA

solution

! R1
no ip route 192.168.10.0 255.255.255.0 198.51.100.2
no ip route 192.168.10.0 255.255.255.0 192.0.2.2 200
ip route 192.168.10.0 255.255.255.0 192.0.2.2
ip route 192.168.10.0 255.255.255.0 198.51.100.2 200

Why this answer

The routing table shows a static route to 192.168.10.0/24 via 198.51.100.2 with Administrative Distance (AD) 1, which is the default for static routes. The intended primary path via 192.0.2.2 was configured with AD 200 (floating static), but because the default AD (1) is lower than 200, the backup route is preferred. The fix is to reconfigure the primary path with the default AD (1) and the backup path with a higher AD (e.g., 200).

This ensures the primary path is used when available and the backup takes over only if the primary fails.

Exam trap

The trap is confusing which route is primary and which is backup. The route with lower AD is preferred, so the backup must have a higher AD. Candidates often misconfigure the AD values, setting the primary with a higher AD.

Why the other options are wrong

Swapping the ADs would keep the backup route preferred, failing to make the primary path active when available.

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230

Multi-Selectmedium

Which two statements accurately describe why BGP is often relevant at an Internet or multi-provider edge?

Select 2 answers

A.It is associated with routing between autonomous systems.

B.It is used for routing between organizations and providers at the network edge.

C.It is mainly used to replace STP on access switches.

D.It is required before DHCP relay can function.

E.It is the protocol used by CAPWAP for AP discovery.

AnswersA, B

BGP (Border Gateway Protocol) is a path-vector protocol designed specifically to exchange network reachability information between autonomous systems (ASes). Its primary role is inter-domain routing, enabling ISPs and large enterprises to make routing decisions based on policies and paths, not just metrics. This distinguishes it from interior gateway protocols (IGPs) like OSPF or EIGRP, which operate within a single AS.

Why this answer

BGP is often relevant at the edge because it is associated with route exchange between autonomous systems and large external routing domains. In practical terms, this makes it a natural protocol to discuss where organizations connect to providers or exchange external reachability. It is not just another interior campus protocol.

The question is about conceptual fit, not deep BGP attribute tuning.

Exam trap

A frequent exam trap is mistaking BGP for an internal protocol or confusing it with unrelated network functions. For example, some might incorrectly believe BGP replaces STP on access switches or is necessary for DHCP relay to work. These are incorrect because BGP operates between autonomous systems for external routing, while STP manages Layer 2 loops and DHCP relay forwards broadcast requests.

Misunderstanding BGP’s scope leads to selecting wrong answers that describe internal or unrelated protocols, so it’s important to focus on BGP’s role in inter-AS routing and external route exchange at the Internet or multi-provider edge.

Why the other options are wrong

Option C is incorrect because BGP does not replace Spanning Tree Protocol (STP). STP is a Layer 2 protocol used to prevent loops in Ethernet networks, whereas BGP is a Layer 3 routing protocol used for inter-AS routing.

Option D is incorrect since DHCP relay functions independently of BGP. DHCP relay forwards DHCP requests across subnet boundaries and does not rely on BGP routing information or sessions to operate.

Option E is incorrect because CAPWAP is a wireless control protocol used for managing access points and is unrelated to BGP or routing protocols used at the Internet edge.

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231

MCQhard

A router has routes to 172.20.0.0/16, 172.20.10.0/24, and 172.20.10.64/26. Which route is used for traffic to 172.20.10.70?

A.172.20.0.0/16

B.172.20.10.0/24

C.172.20.10.64/26

D.The default route

AnswerC

The /26 route wins because longest-prefix match governs forwarding: 172.20.10.70 falls inside 172.20.10.64–172.20.10.127, and /26 is more specific than /24 or /16. The router always selects the longest matching prefix, satisfying the stem's requirement to identify the route actually used.

Why this answer

The /26 route is used because it is the most specific matching prefix. In practical terms, 172.20.10.70 falls inside the 172.20.10.64/26 range, so that route narrows the destination more precisely than the broader /24 and /16 routes. Longest-prefix match therefore selects the /26 entry.

This question is designed to reinforce that specificity comes first in route lookup. Broader routes remain useful, but they lose when a more exact route matches.

Exam trap

A common exam trap is to select a less specific route such as 172.20.0.0/16 or 172.20.10.0/24 because they appear to cover the destination IP 172.20.10.70. Candidates may overlook that the router always prefers the most specific route, which in this case is the /26 subnet. Choosing a broader subnet ignores the longest prefix match principle and leads to incorrect routing decisions.

This trap tests your understanding of how subnet masks influence route selection and the importance of prefix length in Cisco routing tables.

Why the other options are wrong

172.20.0.0/16 is the least specific route covering a large address range. Although it includes 172.20.10.70, it is overridden by more specific subnets like /24 and /26, so it is not used for this destination.

172.20.10.0/24 is more specific than /16 but less specific than /26. Since 172.20.10.70 falls within the /26 subnet, the router prefers the /26 route over this /24 route.

The default route is only used when no other routes match the destination IP. Since multiple specific routes match 172.20.10.70, the default route is not selected.

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232

PBQhard

You are connected to R1. R1 has OSPF configured on GigabitEthernet0/0 with network 10.0.0.0 0.0.0.3 area 1, ip ospf hello-interval 10, and ip ospf dead-interval 40. R2 has OSPF configured on its GigabitEthernet0/0 with network 10.0.0.0 0.0.0.3 area 0, ip ospf hello-interval 5, and ip ospf dead-interval 20. Correct these mismatches so that R1 and R2 become OSPF neighbors.

Network Topology

Hints

•Check the OSPF area configuration on both routers.
•Use 'show ip ospf interface' to compare hello and dead timers.
•The timers must match exactly on both sides of the link.

A.On R1, change the network statement to area 0 and set ip ospf hello-interval 5 and ip ospf dead-interval 20 under the interface.

B.On R2, change the network statement to area 1 and set ip ospf hello-interval 10 and ip ospf dead-interval 40 under the interface.

C.On R1, change the network statement to area 0 and set ip ospf hello-interval 10 and ip ospf dead-interval 40 under the interface.

D.On R2, change the network statement to area 0 and set ip ospf hello-interval 10 and ip ospf dead-interval 40 under the interface.

AnswerA

solution

! R1
configure terminal
router ospf 1
no network 10.0.0.0 0.0.0.3 area 1
network 10.0.0.0 0.0.0.3 area 0
interface gigabitethernet 0/0
ip ospf hello-interval 5
ip ospf dead-interval 20
end

Why this answer

The OSPF adjacency fails due to two mismatches. First, the area is mismatched: R1 uses area 1, R2 uses area 0 (both must be the same area, typically area 0). Second, the hello and dead timers are mismatched: R1 uses Hello 10/Dead 40, R2 uses Hello 5/Dead 20.

To fix, on R1 change the network statement to area 0 and adjust timers to match R2 (or vice versa). The solution below changes R1's area to 0 and sets hello to 5 and dead to 20 to match R2.

Exam trap

The exam trap is that candidates may focus on only one mismatch (area or timers) and forget that both must match. Additionally, they might assume that the router they are connected to should not be changed, or that default timers are always correct. Always verify all OSPF parameters that must match: area ID, hello/dead intervals, network type, and authentication.

Why the other options are wrong

The specific factual error is that the question implies you are connected to R1, so configuring R1 is the expected action. Additionally, using area 1 instead of area 0 is not recommended for a single-area design.

The specific factual error is that the timers are not changed to match R2; they remain at the original values.

The specific factual error is that R2's area is already 0, so changing it to area 0 is redundant. Changing R2's timers to match R1's original timers would still leave a mismatch because R1's timers are not changed.

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233

MCQmedium

What problem do first-hop redundancy protocols such as HSRP solve?

A.They prevent duplicate MAC addresses on a LAN

B.They provide a backup default gateway for end hosts

C.They replace spanning tree on switched networks

D.They encrypt traffic between users and the default gateway

AnswerB

FHRPs such as HSRP create a virtual IP and virtual MAC address that a group of routers share. One router is elected active and forwards traffic, while the standby router takes over seamlessly if the active fails. End hosts are configured with the virtual IP as their default gateway, so they always have a reachable next hop without needing to change their configuration.

Why this answer

First-hop redundancy protocols allow hosts to use a virtual default gateway that can remain available even if one physical router fails.

Exam trap

A frequent exam trap is mistaking HSRP for a protocol that prevents duplicate MAC addresses or replaces Spanning Tree Protocol (STP). While STP prevents Layer 2 loops by blocking redundant paths, HSRP operates at Layer 3 to provide gateway redundancy. Another trap is assuming HSRP encrypts traffic between hosts and routers, which it does not.

Candidates might also confuse HSRP with routing protocols like OSPF or EIGRP, but HSRP only manages default gateway availability, not routing decisions. Understanding these distinctions is crucial to avoid selecting incorrect options that describe unrelated network functions.

Why the other options are wrong

Option A incorrectly states that HSRP prevents duplicate MAC addresses on a LAN. Duplicate MAC address prevention is a function of Layer 2 protocols and network design, not HSRP, which operates at Layer 3 to provide gateway redundancy.

Option C incorrectly claims that HSRP replaces Spanning Tree Protocol (STP). STP prevents Layer 2 switching loops, while HSRP provides Layer 3 gateway redundancy; they serve distinct purposes and coexist in networks.

Option D incorrectly suggests that HSRP encrypts traffic between users and the default gateway. HSRP does not provide encryption; it only manages gateway availability and failover.

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234

MCQmedium

A router has routes for 10.10.0.0/16, 10.10.20.0/24, and a default route. Which route is used for destination 10.10.20.55?

A.The 10.10.0.0/16 route

B.The default route

C.The 10.10.20.0/24 route

D.The router load-balances across all matching routes

AnswerC

The 10.10.20.0/24 route is selected because the router's forwarding decision uses the longest prefix match algorithm. For a destination of 10.10.20.55, this /24 route is the most specific match, covering the exact subnet that contains the address. Even though the default route and the /16 route also match, they have shorter prefixes and are therefore less specific, making the /24 the only candidate used.

Why this answer

The destination matches multiple routes, but the /24 is the most specific match and wins by longest prefix match.

Exam trap

Remember that routers use the longest prefix match rule, not the most general or default route, when multiple routes are available.

Why the other options are wrong

The 10.10.0.0/16 route is broader and encompasses the 10.10.20.0/24 subnet, but it is not the most specific match for the destination 10.10.20.55, which falls under the more specific 10.10.20.0/24 route.

The default route is used only when no more specific routes match the destination address. Since 10.10.20.55 falls within the 10.10.20.0/24 subnet, the default route is not applicable in this case.

This option is wrong because routers do not load-balance across routes unless configured to do so with specific routing protocols or settings. In this case, the most specific route, 10.10.20.0/24, is the only applicable choice for the destination 10.10.20.55.

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235

MCQhard

A router has a static route to 10.30.5.128/25, an OSPF route to 10.30.5.0/24, and a default route 0.0.0.0/0 in its routing table. Which route will the router use for destination 10.30.5.130?

A.The static route to 10.30.5.128/25

B.The OSPF route to 10.30.5.0/24

C.The default route

D.No route, because the destination is outside all prefixes shown.

AnswerA

The router will utilise the static route to 10.30.5.128/25 because it adheres to the longest prefix match principle. This rule dictates that when multiple routes match a destination IP address, the router selects the route with the longest subnet mask, representing the most specific network. For 10.30.5.130, the /25 mask is more specific than the OSPF route's /24 mask or the default route's /0 mask, ensuring it is prioritised for forwarding.

Why this answer

The router selects the route with the longest prefix match between the destination IP and the prefixes in the routing table. 10.30.5.130 matches both 10.30.5.0/24 (prefix length 24) and 10.30.5.128/25 (prefix length 25); the /25 is more specific and wins. Option D is wrong because 10.30.5.130 falls within the subnet range of 10.30.5.128/25 (hosts .129–.254), so a valid route does exist.

Exam trap

Always prioritize the longest prefix match over broader subnets or default routes.

Why the other options are wrong

The OSPF route to 10.30.5.0/24 is less specific than the /25 static route, so the router prefers the longest mask.

The default route (0.0.0.0/0) has the shortest prefix length and would be used only if no other route matches.

10.30.5.130 is inside the 10.30.5.128/25 subnet range, meaning a route exists for this destination.

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236

Multi-Selectmedium

Which TWO statements are true about OSPFv2 neighbor adjacency, network statements, and passive interfaces?

Select 2 answers

A.Configuring an interface as passive stops OSPF from sending Hello packets out of that interface, but OSPF will still advertise the connected network in its LSAs.

B.For two OSPF routers to establish full adjacency, they must agree on the Hello and Dead intervals.

C.The network command with a wildcard mask of 0.0.0.0 will enable OSPF on the exact matching interface, but it will also prevent OSPF from forming adjacencies on that interface.

D.Using the passive-interface default command makes all OSPF interfaces passive, which means OSPF will not advertise any connected networks.

E.The network command with a wildcard mask of 0.0.0.255 area 0 will match any interface whose IP address falls within that /24 subnet, but OSPF will only attempt to form adjacencies on the interface with the highest IP address in that range.

AnswersA, B

The passive-interface command disables Hello transmission on an interface, so no OSPF neighbor can ever be discovered or formed on that segment. However, OSPF's SPF calculation still requires the connected subnet to be known, so the router advertises that network as a stub (Type 1 LSA) within its area. This ensures that remote routers have a route to the subnet, even though no neighbor adjacency exists on the passive interface.

Why this answer

Configuring an interface as passive in OSPFv2 prevents the router from sending Hello packets out of that interface, which stops neighbor discovery and adjacency formation. However, OSPF still includes the connected network of that passive interface in its Type 1 Router LSAs, allowing the network to be advertised to other OSPF routers.

Exam trap

Cisco often tests the misconception that a passive interface stops network advertisement, when in fact it only stops Hello packets and adjacency formation while still advertising the connected network in LSAs.

Why the other options are wrong

A wildcard mask of 0.0.0.0 only matches one exact IP address. It does not impose any restriction on adjacency.

Passive interfaces still advertise their networks—they just do not send or receive Hello packets. Only adjacency is suppressed.

The network command matches multiple interfaces; OSPF then tries to form adjacencies on every enabled interface, regardless of IP address order.

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237

MCQhard

Refer to the exhibit. An engineer expects all traffic destined to the 10.10.10.0 network to be forwarded via 10.1.1.2. However, when testing connectivity to host 10.10.10.64, traffic is being sent to 10.2.2.2 instead. What is the most likely cause?

A.The static route to 10.10.10.0/24 has a higher administrative distance than the /26 route, making the /26 preferred.

B.The router is using longest prefix matching; the /26 route is more specific, so traffic to 10.10.10.64 is forwarded via 10.2.2.2.

C.The /26 static route was configured as a floating static route with an administrative distance of 5, overriding the /24 route.

D.The next-hop 10.1.1.2 for the /24 route is unreachable, causing the router to fall back to the /26 route.

AnswerB

The exhibit shows two overlapping static routes. The /26 prefix length is longer (more specific) than the /24. According to IP routing logic, the router selects the route with the longest matching prefix. The destination 10.10.10.64 falls within the /26 subnet, making it the preferred route.

Why this answer

B is correct because routers use longest prefix matching to forward traffic. The route to 10.10.10.64/26 is more specific (longer prefix length) than the route to 10.10.10.0/24, so even though the /24 route may have a lower administrative distance, the /26 route is preferred for traffic destined to 10.10.10.64. This is a fundamental IP routing principle that overrides administrative distance when both routes exist in the routing table.

Exam trap

Cisco often tests the misconception that administrative distance is the primary tiebreaker for route selection, but the trap here is that longest prefix match is always evaluated first, and only when prefix lengths are equal does administrative distance come into play.

Why the other options are wrong

Misreading the administrative distance value in the routing table; candidates may overlook that both are the same.

Assuming that any backup route must be a floating static, without verifying the actual AD value in the exhibit.

Misconception that a route can be displayed yet be in a 'down' state; in reality, an invalid next-hop prevents the route from being installed.

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238

MCQmedium

A router learns 172.16.40.0/24 from OSPF with AD 110 and metric 20. It also learns the same prefix from EIGRP with AD 90 and feasible distance 30720. Which route is installed?

A.The OSPF route because metric 20 is lower than 30720

B.The EIGRP route because its administrative distance is lower

C.Both routes because ECMP is automatic across different protocols

D.Neither route until one is redistributed into the other protocol

AnswerB

The EIGRP route is installed because Cisco routers compare administrative distance (AD) before any metric when two different routing protocols advertise the same prefix. OSPF has a default AD of 110, while EIGRP's default AD is 90, making EIGRP more trustworthy. Since the router selects the route with the lowest AD, the EIGRP route wins regardless of its metric value. Metrics are only compared among routes from the same protocol.

Why this answer

When the same prefix is learned from different routing protocols, the router compares administrative distance first. EIGRP internal routes have AD 90, which beats OSPF AD 110, so the EIGRP path goes into the table.

Exam trap

A frequent exam trap is assuming that the route with the lower metric value is always preferred, regardless of the routing protocol. In this question, the OSPF route has a metric of 20, which seems better than EIGRP's feasible distance of 30720. However, Cisco routers do not compare metrics across different protocols.

Instead, they rely on administrative distance to choose the best route. Mistaking metric comparison for cross-protocol route selection can lead to choosing the wrong answer and misunderstanding how Cisco routing decisions work.

Why the other options are wrong

This option incorrectly assumes that the router compares OSPF metric 20 directly against EIGRP feasible distance 30720 to select the route. Cisco routers do not compare metrics across different routing protocols; they use administrative distance first. Therefore, this option is incorrect.

This option incorrectly claims that both routes are installed due to automatic ECMP across different protocols. Cisco routers do not perform equal-cost load balancing between different routing protocols without explicit redistribution or configuration, so this is false.

This option incorrectly states that neither route is installed until redistribution occurs. Redistribution is not necessary for a router to install a route learned from a routing protocol. The router installs the route with the lowest administrative distance immediately, so this option is incorrect.

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239

MCQmedium

A router interface is configured for OSPF, but neighbors do not form. The engineer checks the interface and sees Hello 10 and Dead 40. The neighbor on the same segment uses Hello 30 and Dead 120. What is the most likely cause of the OSPF adjacency failure?

A.Router IDs are identical

B.OSPF timers do not match

C.The interface cost is too low

D.The subnet mask is invalid because it is a transit link

AnswerB

Correct. This is correct. OSPF neighbors must agree on timer values such as hello and dead intervals. If they do not, the devices will not form a full adjacency even if other parts of the link appear healthy.

Why this answer

The adjacency fails because the OSPF hello and dead timers do not match. OSPF neighbors on the same segment must agree on several key parameters before they accept each other as neighbors, and the timer settings are one of those required matches. In plain terms, each router is expecting to hear OSPF hellos at one rhythm, but the other side is speaking at a different rhythm, so the relationship never becomes valid.

This is different from cost, which matters later during path selection after neighbors are already exchanging information. The timer mismatch is a classic CCNA troubleshooting point because the interfaces can be up and IP connectivity can even appear normal while the OSPF adjacency still fails.

Exam trap

Be cautious of confusing OSPF timer mismatches with other common OSPF configuration issues like network types or authentication.

Why the other options are wrong

This option is wrong because OSPF allows multiple routers to have the same Router ID, but they can still form adjacencies if other parameters are correctly configured. The issue in this scenario is related to mismatched OSPF timers, not Router IDs.

This option is incorrect because the interface cost does not directly affect the formation of OSPF adjacencies; it only influences the route selection process once adjacencies are established.

The subnet mask being invalid is not the cause of the OSPF adjacency failure in this scenario, as the issue lies with the mismatch of OSPF timers rather than an incorrect subnet mask. Both routers are on the same segment and should have compatible subnet configurations.

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240

MCQhard

A router has these routes installed. Which path will be chosen for traffic to 172.16.10.200?

A.O 172.16.10.0/24 via 10.1.1.2

B.S 172.16.10.128/25 via 10.1.1.6

C.O 172.16.0.0/16 via 10.1.1.10

D.S* 0.0.0.0/0 via 203.0.113.1

AnswerB

The static route to 172.16.10.128/25 is selected because it offers the longest prefix match (25 bits) for the destination 172.16.10.200, which lies within the 172.16.10.128–172.16.10.255 range. Cisco routers always prefer the route with the greatest number of matching bits, so this /25 route outranks the /24 and /16 OSPF routes and the default route, regardless of administrative distance or metric. Traffic is therefore forwarded to next-hop 10.1.1.6.

Why this answer

When multiple routes could match a destination, the router first uses longest-prefix match. In plain language, it chooses the route that describes the destination most specifically, not simply the one from the protocol with the lowest metric somewhere else in the table. For 172.16.10.200, the key is to determine which listed prefix actually contains that address and is the narrowest valid match.

If a /25 and a /24 both match, the /25 wins because it is more specific. If the destination does not fit inside the smaller subnet, then the broader route is used instead. That is the entire skill being tested here: careful evaluation of the prefix boundaries before thinking about anything else. Once you recognize the address falls within the upper half of the /24, the more specific route becomes obvious.

Exam trap

A frequent exam trap is to select a route based solely on the routing protocol type or administrative distance without verifying the subnet mask specificity. For example, candidates might incorrectly choose the OSPF-learned /24 route over the static /25 route because they assume dynamic routes are preferred or because they overlook the subnet boundaries. This mistake ignores the fundamental longest-prefix match rule, which always prioritizes the most specific subnet regardless of protocol.

Misreading subnet ranges or confusing the address boundaries of a /25 versus a /24 can also lead to choosing an incorrect route.

Why the other options are wrong

Option A shows an OSPF route to 172.16.10.0/24 via 10.1.1.2. Although the /24 subnet covers 172.16.10.200, it is less specific than the /25 subnet. Therefore, this route will not be chosen because the router prefers the more specific /25 route.

Option C shows an OSPF route to 172.16.0.0/16 via 10.1.1.10. This is a very broad subnet covering a large address range, including 172.16.10.200. However, since more specific routes exist (/24 and /25), this route will be ignored in favor of the longer prefix matches.

Option D is a static default route (0.0.0.0/0) via 203.0.113.1. Default routes are only used when no other more specific route matches the destination. Since the /25 route matches 172.16.10.200, the default route will not be selected.

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241

MCQmedium

Why is route summarization useful at a distribution layer or area boundary?

A.It reduces the number of specific prefixes that must be carried or advertised.

B.It forces all traffic to use a default route only.

C.It automatically encrypts routing updates.

D.It removes the need for subnetting.

AnswerA

Route summarization aggregates multiple contiguous subnets into a single less-specific prefix, such as advertising 10.1.0.0/16 instead of dozens of /24s. At the distribution layer, this dramatically reduces the number of prefix entries that must be stored in routing tables and included in routing updates, lowering memory and bandwidth consumption. It also limits route flapping because a summary only changes when the underlying aggregated block's reachability changes, not when individual subnets oscillate.

Why this answer

Route summarization is useful because it reduces the number of individual routes that have to be advertised and stored. In practical terms, one summary can represent many more specific internal prefixes, which helps keep routing tables smaller and updates simpler. That improves scalability and reduces control-plane clutter.

Summarization does not eliminate the need for detail everywhere, but it helps present the network more efficiently at aggregation points.

Exam trap

A frequent exam trap is mistaking route summarization for default routing or encryption. Some candidates incorrectly believe summarization forces all traffic to use a default route or that it secures routing updates by encrypting them. Neither is true.

Summarization simply aggregates multiple specific routes into fewer, broader prefixes to reduce routing table size and update complexity. Misunderstanding this can lead to selecting incorrect answers such as options B or C, which confuse summarization with unrelated routing concepts. Recognizing that summarization optimizes routing information without changing traffic forwarding behavior or security is essential to avoid this trap.

Why the other options are wrong

This option is incorrect because summarization does not force all traffic to use a default route. Summarization aggregates routes but does not replace them with a default route, so traffic forwarding decisions remain based on specific or summarized routes.

This option is wrong as route summarization does not provide encryption for routing updates. Encryption is a separate security feature unrelated to summarization, which only aggregates routing information.

This option is incorrect because summarization does not remove the need for subnetting. Subnetting defines network address structure, while summarization aggregates existing subnets into broader prefixes for routing efficiency.

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242

MCQhard

A static default route is configured with an administrative distance of 250. What is the most likely design intention?

A.To keep the route as a backup of last resort behind normal learned routes

B.To make the route override all dynamic routing immediately

C.To disable default routing entirely

D.To convert the default route into a host route

AnswerA

Administrative distance 250 exceeds the default values for connected, static, EIGRP, OSPF and RIP routes, so the static default only enters the routing table when all preferred routes fail. This deliberately makes it a floating static backup of last resort.

Why this answer

The design intention is to make the static default route a very low-priority backup path. In plain language, the administrator wants the route to exist only as a last resort behind almost any normal learned path. By assigning such a high administrative distance, the route stays out of the active table unless better routes disappear.

This is a floating-static design concept. The route is not meant to be primary. It is intentionally configured to sit in reserve and become relevant only during failure conditions or severe loss of normal routing information.

Exam trap

A common exam trap is assuming that increasing the administrative distance disables the static route or forces it to override dynamic routes. In reality, a higher AD causes the static route to be less preferred, effectively floating it behind all other routes. Candidates might confuse the AD value with route priority or think that setting it to 250 disables the route, but the route remains active and is used only as a last resort.

Misinterpreting this can lead to incorrect answers about route behavior and fail to recognize the floating static route design pattern.

Why the other options are wrong

Incorrect. A high administrative distance does not make a route override dynamic routes; it makes the route less preferred. Therefore, the static route will not immediately override dynamic routes.

Incorrect. Assigning a high administrative distance does not disable the route; it remains configured and available as a backup. The route is not conceptually disabled but deprioritized.

Incorrect. Administrative distance affects route preference, not the route prefix or mask. Changing AD does not convert a default route into a host route.

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243

PBQhard

You are connected to R1 via the console. Configure single-area OSPFv2 on R1, R2, and R3 so that all three routers can exchange routes. The current configuration has mismatched hello/dead timers on the link between R1 and R2, and an area mismatch on the link between R2 and R3. Correct these issues and ensure OSPF adjacencies form.

Network Topology

Hints

•Check the hello/dead timers on R2's G0/0 using 'show ip ospf interface'.
•Check the OSPF area on R2's G0/1 and R3's G0/1 using 'show ip ospf interface'.
•On R2, use 'ip ospf hello-interval' and 'ip ospf dead-interval' under G0/0, and 'network' command under router ospf to change area.

A.On R2, configure interface G0/0 with 'ip ospf hello-interval 10' and 'ip ospf dead-interval 40', and modify the OSPF network statement for 10.0.23.0/30 to area 0.

B.On R2, configure interface G0/0 with 'ip ospf hello-interval 30' and 'ip ospf dead-interval 120', and modify the OSPF network statement for 10.0.23.0/30 to area 1.

C.On R1, configure interface G0/0 with 'ip ospf hello-interval 30' and 'ip ospf dead-interval 120', and on R3, change the OSPF network statement for 10.0.23.0/30 to area 1.

D.On R1, configure interface G0/0 with 'ip ospf hello-interval 10' and 'ip ospf dead-interval 40', and on R2, modify the OSPF network statement for 10.0.23.0/30 to area 1.

AnswerA

solution

! R1

Why this answer

The adjacency between R1 and R2 fails because R1 has hello/dead timers of 10/40, while R2 has 30/120 on G0/0. The adjacency between R2 and R3 fails because R2's G0/1 is in area 1, but R3's G0/1 is in area 0. On R2, change the hello/dead timers on G0/0 to match R1 (10/40) using 'ip ospf hello-interval 10' and 'ip ospf dead-interval 40'.

Also change the network statement for 10.0.23.0/30 to area 0 using 'network 10.0.23.0 0.0.0.3 area 0'. Verify with 'show ip ospf neighbor' on all routers.

Exam trap

A common trap is to assume that timers must be changed on the router with the 'non-default' values, but OSPF requires timers to match on both ends; either router can be adjusted. Another trap is to think that the area mismatch can be resolved by changing the area on either router, but the correct area must be consistent with the network design. In this scenario, the existing explanation specifies the correction on R2.

Why the other options are wrong

The specific factual error is that the timers should be made consistent by adjusting R2 to match R1, not the other way around, and the area mismatch requires both routers to be in the same area, which is area 0.

The specific factual error is that the timers can be adjusted on either router, but the area mismatch must be resolved by making both routers use the same area. Changing R3 to area 1 would not fix the adjacency if R2 is already in area 1? Actually, R2 is in area 1 on G0/1, so changing R3 to area 1 would make them match, but the question states the area mismatch is on the link between R2 and R3, and the existing explanation says to change R2's network statement to area 0. This option changes R3 instead, which could also work, but the question expects the correction on R2 as per the existing explanation.

Additionally, changing R1's timers is not the most efficient if R1 is already configured correctly.

The specific factual error is that the timers on R1 are already correct, and the area mismatch requires both routers to be in the same area. Changing R2's area to area 1 would not match R3's area 0.

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244

Multi-Selectmedium

Which two statements accurately describe passive interfaces in OSPF?

Select 2 answers

A.It suppresses OSPF hello packets on that interface.

B.It can still allow the connected network to be advertised into OSPF.

C.It converts OSPF on that interface into static routing.

D.It forces the interface IP address to become the router ID.

E.It disables OSPF on every interface in the router automatically.

AnswersA, B

Passive-interface in OSPF stops the router from sending or processing OSPF hello packets on that specific interface. Because hello packets are how neighbor adjacencies are discovered and maintained, the router will not form OSPF neighbors on that link, effectively preventing dynamic neighbor relationships while leaving the interface operational.

Why this answer

A passive interface stops the router from sending OSPF hello packets on that interface, which means the router will not try to form neighbors there. In practical terms, this is useful on user-facing or stub-like links where no OSPF neighbor should exist. However, passive does not necessarily mean the connected network disappears from OSPF. The network can still be advertised through the router’s other active adjacencies.

This is a common design and security practice because it reduces unnecessary routing chatter on interfaces that should not form adjacencies in the first place.

Exam trap

A frequent exam trap is assuming that configuring an interface as passive disables OSPF routing on that interface or converts OSPF routes into static routes. Candidates may also mistakenly believe that passive interfaces automatically disable OSPF on all router interfaces or force the interface IP to become the router ID. These misunderstandings arise because passive interfaces stop hello packets but do not disable OSPF or affect router ID selection.

Misreading this can lead to incorrect answers about OSPF behavior and network design.

Why the other options are wrong

Option C is incorrect because passive interfaces do not convert OSPF into static routing; OSPF remains active and continues to advertise routes.

Option D is incorrect because passive interface configuration does not influence router ID selection, which is determined by other OSPF rules.

Option E is incorrect because passive interface settings apply only to the specified interface and do not disable OSPF on all router interfaces.

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245

MCQhard

Exhibit: R3 learns 10.50.0.0/16 by OSPF through two equal-cost paths. What will R3 do by default?

A.Install both routes and load balance

B.Choose the route from the neighbor with the highest router ID only

C.Install only one route because OSPF does not support ECMP

D.Prefer the path with the lower next-hop IP address

AnswerA

OSPF's cost-based shortest path algorithm can yield multiple paths with identical metric to the same destination. By default, the router installs all such equal-cost paths into its routing table, up to the maximum-paths limit, and load balances traffic across them. Since both paths are equal cost, the router does not pick one over the other; it uses them together for traffic sharing.

Why this answer

When OSPF has equal-cost routes to the same destination, the router installs multiple paths and can load balance across them, assuming the platform supports the default maximum-paths value.

Exam trap

A frequent exam trap is believing that OSPF will choose only one route when multiple equal-cost paths exist, often assuming it picks the route from the neighbor with the highest router ID or the path with the lowest next-hop IP address. This misconception leads to incorrect answers because OSPF’s path selection process installs all equal-cost routes by default. Misunderstanding this behavior can cause candidates to overlook OSPF’s load balancing capability and mistakenly select options that describe single-route preferences, which do not apply to equal-cost multipath scenarios.

Why the other options are wrong

Incorrect because OSPF does not select a single route based on the highest router ID when multiple equal-cost paths exist; it installs all such routes.

Incorrect because OSPF explicitly supports equal-cost multipath (ECMP) routing and does not limit itself to installing only one route.

Incorrect because the next-hop IP address is not a factor in OSPF’s path selection among equal-cost routes; cost metric is the deciding factor.

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246

MCQhard

A branch router uses PPP on a serial WAN link. Which additional PPP capability most directly improves access security on that link?

A.PPP authentication

B.STP root election

C.Wireless roaming

D.IPv6 loopback addressing

AnswerA

PPP authentication is correct because the Point-to-Point Protocol includes native authentication mechanisms—PAP and CHAP—that let a branch router verify the identity of the remote peer on a serial WAN link. CHAP performs a three-way handshake with a challenge and a hashed response, while PAP sends the credentials in plaintext, so CHAP is the more secure choice. This peer-identity verification is an inherent PPP security capability that directly answers what additional functionality the router gains.

Why this answer

PPP authentication most directly improves access security on the link. In practical terms, authentication helps verify the identity of the peer rather than simply bringing up the point-to-point connection without validation. That makes PPP more useful than a bare unauthenticated link in environments where peer identity matters.

At CCNA level, the important point is recognizing that PPP is associated with optional authentication capability on WAN links.

Exam trap

A common exam trap is selecting options like STP root election or IPv6 loopback addressing as security features for PPP links. STP is a Layer 2 protocol that prevents loops in Ethernet networks and does not apply to serial WAN links or PPP authentication. Similarly, IPv6 loopback addresses are used for router management and diagnostics, not for authenticating peers on a WAN link.

Candidates may also be tempted by unrelated wireless concepts like roaming, which have no bearing on PPP serial link security. Recognizing that PPP authentication specifically addresses peer verification on point-to-point links is essential to avoid these distractions.

Why the other options are wrong

STP root election is incorrect because STP operates at Layer 2 to prevent loops in Ethernet networks and does not provide authentication or security on PPP serial links.

Wireless roaming is unrelated to serial WAN links and PPP authentication; it applies to wireless LAN environments and does not affect WAN link security.

IPv6 loopback addressing is used for router management and diagnostics and does not provide any authentication or security features for PPP WAN links.

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247

MCQhard

A router has a default route and a specific route to 203.0.113.0/24. Which route is used for traffic to 203.0.113.25?

A.The specific route to 203.0.113.0/24

B.The default route

C.Both routes are always load-balanced

D.Neither route because defaults cannot coexist with specific routes

AnswerA

Longest-prefix match governs Cisco route selection: 203.0.113.0/24 has a 24-bit prefix, exceeding the default route's 0-bit prefix, so the router forwards traffic to 203.0.113.25 via the specific route. Administrative distance and metric are only compared between routes sharing the same prefix length, so neither affects this decision.

Why this answer

The specific route to 203.0.113.0/24 is used because it is a more specific match than the default route. In plain language, even though the default route could technically match almost anything, the router always prefers a route that more precisely describes the destination network. Since 203.0.113.25 is inside 203.0.113.0/24, that route wins under longest-prefix match.

This is one of the most basic routing-table interpretation rules. The default route remains important as a fallback, but it is not chosen when a more specific valid route exists.

Exam trap

Remember that the router always prefers the most specific route, not the default route, when a specific match is available.

Why the other options are wrong

The default route is used for traffic to destinations not explicitly defined in the routing table. Since there is a specific route to 203.0.113.0/24, that route will take precedence for traffic to 203.0.113.25.

This option is incorrect because routing protocols do not load-balance traffic between a specific route and a default route; the more specific route will always take precedence for matching traffic.

This option is wrong because default routes can coexist with specific routes; the router will prioritize the specific route to 203.0.113.0/24 for traffic to 203.0.113.25.

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248

Multi-Selectmedium

A network engineer needs a floating static route to back up an OSPF-learned route. Which two configurations are necessary for the static route to remain unused until OSPF fails?

Select 2 answers

A.Configure the static route with an administrative distance higher than 110

B.Point the static route toward a valid next-hop or exit interface

C.Set the static route metric lower than the OSPF cost

D.Configure the route as directly connected with no next-hop information

AnswersA, B

A floating static route must be less preferred than the OSPF-learned route while OSPF is operational. Since OSPF has an administrative distance of 110, the competing static route should be configured with an AD greater than 110 (e.g., 120), making it a backup that is used only when OSPF disappears. This allows the route to remain in the configuration but not in the routing table during normal OSPF operation.

Why this answer

A floating static route requires an administrative distance higher than OSPF's default of 110 (option A) so that the static route is less preferred and remains inactive while OSPF is available. Additionally, the static route must point to a valid next-hop IP or exit interface (option B); without a valid next-hop, the route cannot be installed in the routing table and would never serve as a backup. Option C is incorrect because Cisco routers compare administrative distance before metric when routes come from different sources, so a lower metric cannot override the AD difference.

Option D is wrong because a directly connected route (with no next-hop) would be treated as a connected route, not a static route, and would be preferred over OSPF due to its AD of 0, defeating the purpose of a floating backup.

Exam trap

A common mistake is assuming that lowering the static route's metric makes it preferred, but Cisco routers compare administrative distance before metric when routes originate from different sources.

Why the other options are wrong

Setting the static route metric lower than the OSPF cost is ineffective because Cisco routers compare administrative distance first across different routing sources.

Configuring the route as directly connected with no next-hop information would give it an administrative distance of 0, making it preferred over OSPF, which is not the behavior of a floating static route.

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249

MCQmedium

Exhibit: R1 has learned 10.50.0.0/24 through OSPF and also has a floating static route to the same prefix with administrative distance 130. Which route is installed while OSPF is healthy?

A.The static route because static routes always win over dynamic routes

B.The OSPF route because its administrative distance is lower than the floating static route

C.Both routes because the prefix length matches

D.Neither route until equal-cost load balancing is configured

AnswerB

The OSPF route is preferred because Cisco routers select the route with the lowest administrative distance when multiple routing protocols or static routes provide the same prefix. OSPF has an AD of 110, while the floating static route is intentionally configured with an AD of 130 (higher than the default static AD of 1) to act as a backup. Since 110 < 130, the router installs the OSPF route in the routing table and keeps the static route in standby until OSPF fails.

Why this answer

A floating static route is meant to stay out of the table until the preferred route disappears. OSPF has administrative distance 110, which is lower than the static route AD 130, so the OSPF route is installed while the OSPF path is still present.

Exam trap

Remember that administrative distance determines route preference. A lower value means higher preference.

Why the other options are wrong

This option is incorrect because static routes do not always win over dynamic routes; the route with the lowest administrative distance is preferred. In this case, OSPF has a lower administrative distance (110) than the floating static route (130).

This option is incorrect because only one route can be installed in the routing table for a specific prefix, and in this case, OSPF has a lower administrative distance than the floating static route, so only the OSPF route will be installed.

This option is incorrect because OSPF is healthy and has a lower administrative distance than the floating static route, meaning the OSPF route will be preferred and installed in the routing table.

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250

Drag & Dropmedium

Drag and drop the following steps into the correct order to configure HSRP on a Cisco IOS-XE router, including priority, preempt, virtual IP, and then verify the active/standby election and failover process.

Drag or tap steps into the slots.

Steps

Order

1Step 1

2Step 2

3Step 3

4Step 4

Why this order

First, the interface is configured. Then the virtual IP is set, followed by priority and preempt. Verification confirms the election, and failover testing demonstrates the preempt mechanism works.

Exam trap

The exam trap is that candidates often confuse the order of priority and preempt, or try to configure HSRP parameters before the interface is ready. Remember: interface first, then virtual IP, then priority, then preempt. Verification and testing come last.

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251

Multi-Selectmedium

Which two statements accurately describe floating static routes?

Select 2 answers

A.They are static routes configured with higher administrative distance so they act as backups.

B.They can become active automatically if the preferred route is lost.

C.They always override dynamic routes immediately.

D.They are identical to equal-cost load balancing.

E.They remove the need for routing tables.

AnswersA, B

A floating static route is a static route manually configured with an administrative distance higher than that of the primary route (e.g., 150 instead of 110 for OSPF). This elevated AD prevents it from being installed in the routing table while the preferred route is present, ensuring it serves solely as a backup entry.

Why this answer

The two correct statements describe floating static routes as backup routes with higher administrative distance that activate when the preferred route is lost. Option C is wrong because floating static routes have a higher administrative distance, so they do not override dynamic routes immediately; they only activate if the dynamic route is lost. Option D is wrong because floating static routes are for backup, not equal-cost load balancing.

Option E is wrong because floating static routes are entries in the routing table that provide backup, not a replacement for it.

Exam trap

Be cautious of confusing floating static routes with load balancing or manual intervention requirements.

Why the other options are wrong

Floating static routes have higher administrative distance, so they do not override dynamic routes immediately.

Floating static routes are for backup purposes, not equal-cost load balancing.

Floating static routes are entries in the routing table, not a replacement for it.

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252

MCQhard

Two routers are in the same OSPF area and on the same subnet, but they do not form an adjacency. One interface uses a hello interval of 10 seconds and the other uses 5 seconds. What is the most likely cause?

A.The OSPF hello timers do not match.

B.The routers need matching hostnames.

C.The subnet must be changed to /24 before OSPF can work.

D.The routers must both use static routes first.

AnswerA

OSPF requires neighboring routers to agree on hello and dead intervals to form and maintain adjacency. If hello timers do not match, the router will not accept the neighbor's Hello packets within the dead interval, causing the Dead Timer to expire and preventing adjacency. This specific mismatch is a classic cause when two routers are in the same area and subnet but cannot see each other as OSPF neighbors.

Why this answer

An OSPF timer mismatch is the most likely cause. In plain language, the routers are trying to discover each other, but they are speaking on different timing expectations. OSPF neighbors on the same segment must agree on certain parameters before they trust each other enough to form an adjacency, and the hello and dead timers are among those critical values.

This is a very common OSPF troubleshooting issue because the interfaces may still be reachable with ping and may even appear correctly addressed and placed in the same area. But OSPF is stricter than simple IP reachability. If the hello interval does not match, the adjacency usually fails before it becomes fully operational.

Exam trap

A common exam trap is assuming that because two routers can ping each other on the same subnet, their OSPF adjacency will form automatically. The trap lies in overlooking the importance of matching OSPF hello and dead timers. Many candidates focus only on IP addressing or area configuration and miss that OSPF requires exact timer agreement.

This leads to confusion when adjacency never forms despite correct IP setup. The exam tests your understanding that OSPF is a protocol with strict neighbor parameter requirements, not just IP reachability.

Why the other options are wrong

Incorrect because router hostnames do not affect OSPF adjacency formation. OSPF neighbors identify each other by router IDs and interface parameters, not hostnames.

Incorrect because OSPF supports various subnet masks and does not require a /24 subnet. The problem is related to timer mismatch, not subnet size.

Incorrect because static routes are not necessary for OSPF adjacency. OSPF dynamically discovers neighbors using hello packets and forms adjacencies based on protocol parameters.

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253

MCQmedium

You are configuring a default route on R1 to send all unknown traffic to the next-hop 203.0.113.1. However, you want this route to be used only if the primary default route learned via OSPF is unavailable. Which command should you use?

A.ip route 0.0.0.0 0.0.0.0 203.0.113.1

B.ip route 0.0.0.0 0.0.0.0 203.0.113.1 200

C.ip route 0.0.0.0 0.0.0.0 203.0.113.1 255

D.ip route 0.0.0.0 0.0.0.0 203.0.113.1 110

AnswerB

This command configures a floating static default route with an administrative distance of 200. Since OSPF's administrative distance is 110, the static route will not be installed in the routing table as long as the OSPF default route is present. If the OSPF route is lost, the static route becomes active, providing backup connectivity. This is the correct way to configure a backup default route.

Why this answer

A floating static route is configured with an administrative distance higher than the primary route's administrative distance. OSPF has a default administrative distance of 110, so setting the static route to 200 ensures it is only used when the OSPF route is not available. This provides a backup path without interfering with normal operation.

Exam trap

The trap here is using an administrative distance that is too low or equal to the primary route, which would cause the static route to be preferred or create ambiguity.

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254

Multi-Selectmedium

A branch router is running single-area OSPF. An engineer wants an interface to advertise its connected network into OSPF but must prevent hello packets from being sent on that LAN segment. Which two actions achieve that goal?

Select 2 answers

A.Enable OSPF on the interface or matching network statement

B.Configure the interface as passive in the OSPF process

C.Set the interface network type to point-to-point

D.Apply distribute-list out on the interface

AnswersA, B

Enabling OSPF on an interface directly using `ip ospf <process-id> area <area-id>` or via a `network` statement under the OSPF process configuration ensures the connected network is advertised into the OSPF routing domain. This action directly satisfies the requirement to advertise the interface's connected network into OSPF, forming one part of the overall solution.

Why this answer

In OSPF, a passive interface still advertises the connected network but does not send or process hello packets. So the interface must participate in OSPF, and then it must be made passive.

Exam trap

A frequent exam trap is assuming that changing the OSPF network type or applying a distribute-list on the interface will stop hello packets. Many candidates mistakenly believe that setting the interface to point-to-point suppresses hellos, but it only changes adjacency behavior. Similarly, distribute-lists filter routing updates but do not affect hello packet transmission.

The key mistake is forgetting that OSPF must be enabled on the interface to advertise the network and that only the passive-interface command prevents hello packets while still advertising the connected subnet.

Why the other options are wrong

Setting the interface network type to point-to-point changes adjacency behavior but does not suppress hello packets. Therefore, it does not meet the requirement to prevent hello packet transmission.

Applying a distribute-list out on the interface filters routing updates but does not affect the sending of OSPF hello packets. It does not prevent hello packet transmission on the LAN segment.

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255

Multi-Selecthard

Exhibit: A static route to 172.16.40.0/24 is configured, but traffic still follows the default route. Which two explanations are plausible?

Select 2 answers

A.The next hop for the static route may not be reachable

B.The exit interface associated with that path may be down

C.The default route always overrides more specific routes

D.Static routes require a metric lower than 1

E.The destination prefix must be configured under router ospf first

AnswersA, B

When a static route is configured with only a next-hop IP address, the router must perform a recursive route lookup to determine the exit interface and next-hop reachability. If that next-hop IP is not reachable—meaning there is no valid route in the routing table to that IP—the static route will not be installed in the routing table. This commonly happens when the next hop is on a directly connected network that is down or has no matching connected route.

Why this answer

If a static route points to an unreachable next hop or the outgoing interface is down, the route may not be installed as usable. In that case the router can still use a less specific route such as the default route.

Exam trap

A frequent exam trap is believing that a static route always takes precedence over a default route regardless of network conditions. Candidates may overlook that Cisco routers require the next hop to be reachable and the exit interface to be operational before installing the static route. If these conditions are not met, the router ignores the static route and uses the default route instead.

This misunderstanding can lead to incorrect answers, especially when the question involves static route reachability or interface status.

Why the other options are wrong

Incorrect because Cisco routers use the longest prefix match rule, meaning a more specific static route overrides the default route when valid. The default route does not always override specific routes.

Incorrect because static routes do not require a metric lower than 1. Static routes have an administrative distance of 1 by default, but metric values do not prevent route installation based on reachability.

Incorrect because static routes operate independently of dynamic routing protocols like OSPF. The destination prefix does not need to be configured under OSPF for a static route to function.

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256

MCQhard

On a broadcast multiaccess segment, R3 has an OSPF priority of 255, but it is in the DROTHER state. Which explanation best fits OSPF behavior?

A.DR election is nonpreemptive on broadcast networks

B.A router cannot become DR if it uses a loopback router ID

C.OSPF priority works only on point-to-point links

D.R3's priority is lower than the current DR's priority

AnswerA

DR/BDR election is nonpreemptive on broadcast multiaccess networks: once the DR and BDR are elected, they remain in those roles until they fail or the OSPF process/interface is reset. Increasing a router's OSPF priority after the election (as with R3) does not force a new election, so the existing DR stays active even if R3 now has a higher priority. To replace the DR, you must clear the OSPF process or reload the router, not just adjust priority.

Why this answer

On broadcast networks, OSPF DR and BDR election is not preemptive. If a DR is already elected, giving another router a higher priority later does not force a new election unless the current DR goes down or OSPF is reset on the segment.

Exam trap

A common exam trap is assuming that increasing a router's OSPF priority after the DR election will cause it to immediately become the new DR. Many candidates mistakenly believe OSPF DR election is preemptive and that the router with the highest priority always becomes DR instantly. However, OSPF DR election on broadcast networks is nonpreemptive, meaning the current DR remains until it fails or OSPF adjacency resets.

This misunderstanding can lead to incorrect answers about why a router with a higher priority remains DROTHER, as in the case of R3 in the question.

Why the other options are wrong

This distractor assumes the election is based on current priority values, but OSPF DR election is nonpreemptive; even if R3's priority is higher, it will not become DR unless the current DR fails.

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257

Drag & Dropmedium

Drag and drop the following steps into the correct order to configure single‑area OSPFv2 on a router, advertise the 192.168.10.0/24 and 10.0.0.0/24 networks in area 0, and set the GigabitEthernet0/0 interface as passive.

Drag or tap steps into the slots.

Steps

Order

1Step 1

2Step 2

3Step 3

4Step 4

5Step 5

6Step 6

Why this order

The correct sequence is: (1) Enter global configuration mode with 'configure terminal' – this is required before any configuration commands. (2) Initiate the OSPF process with 'router ospf 1' – this places the CLI into OSPF router configuration mode where the remaining commands are issued. (3) Advertise the 192.168.10.0/24 network in area 0 – the 'network' command must be issued under OSPF router mode to inject the connected network into OSPF. (4) Advertise the 10.0.0.0/24 network – a second 'network' statement; the order of network commands is interchangeable but they must be configured before setting passive interfaces in a logical workflow. (5) Configure GigabitEthernet0/0 as a passive interface – this prevents OSPF Hello packets and neighbor adjacency on that interface while still advertising its subnet, and it is configured under OSPF router mode. (6) Return to privileged EXEC mode with 'end' – exits configuration mode and returns to the enable prompt. While setting a passive interface before the network statement does not break the configuration, Cisco documentation suggests adding networks first to clearly define which interfaces participate in OSPF before applying passive-interface restrictions.

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258

Multi-Selectmedium

Which TWO statements accurately describe the behavior and configuration of floating static routes?

Select 2 answers

A.A floating static route is configured with a lower administrative distance than the primary dynamic route.

B.A floating static route uses an administrative distance greater than that of the primary dynamic route.

C.The administrative distance of a floating static route must be less than 1.

D.A floating static route becomes active only when the primary route is removed from the routing table.

E.Floating static routes automatically adjust their administrative distance based on network conditions.

AnswersB, D

This is the fundamental characteristic of a floating static route. By assigning an AD higher than the primary route's AD, the static route becomes less preferred, so it will not appear in the routing table while the dynamic route is alive. A typical example is configuring a static route with AD 150 when OSPF is running at AD 110; the static route only takes over if the OSPF route is withdrawn. This mechanism allows the router to automatically switch to a backup path when the primary path is lost.

Why this answer

A floating static route serves as a backup by being configured with an administrative distance (AD) greater than that of the primary dynamic route, making it less preferred (option B). It remains inactive until the primary route is removed from the routing table, at which point the floating static route is installed (option D). Option A is wrong because it reverses the AD logic—a floating static route uses a higher, not lower, AD.

Option C is incorrect because the AD of a floating static route is typically a value between 1 and 255, not necessarily less than 1. Option E is false because the AD of a floating static route is a fixed configured value and does not change automatically based on network conditions.

Exam trap

Cisco often tests the misconception that a floating static route uses a lower AD to 'float' above the primary route, when in fact it uses a higher AD to remain inactive until the primary route is lost.

Why the other options are wrong

A lower AD would make the static route preferred over the dynamic route, not floating.

AD values are integers; 0 is directly connected, and 1 is static. A floating static route must be >1 to be less preferred than a static default.

AD is a static value set at configuration time; it does not auto-adjust.

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259

MCQeasy

A network administrator needs to configure a static route on a Cisco router to reach the 192.168.50.0/24 network through next-hop 10.1.1.2. Which command accomplishes this?

A.ip route 192.168.50.0 255.255.255.0 10.1.1.2 1

B.ip route 192.168.50.0/24 10.1.1.2

C.ip route 192.168.50.0 255.255.255.0 10.1.1.2

D.ip route 192.168.50.0 255.255.255.0 Ethernet0/0 10.1.1.2

AnswerC

This command specifies the destination network 192.168.50.0, the subnet mask 255.255.255.0, and the next-hop address 10.1.1.2. This is the correct syntax for an IPv4 static route on Cisco IOS and will install the route in the routing table if the next hop is reachable.

Why this answer

The correct syntax for an IPv4 static route on Cisco IOS is 'ip route destination_network subnet_mask next_hop_address'. The destination network and mask must be in dotted-decimal format, and the next-hop address is the IP address of the adjacent router. This command creates a static route to 192.168.50.0/24 via 10.1.1.2.

Exam trap

The trap here is using CIDR notation like /24 in the ip route command, which is not supported in Cisco IOS for static route configuration.

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260

MCQhard

A network engineer is troubleshooting an OSPFv3 adjacency issue between two directly connected routers. Both routers are configured for OSPFv3 in area 0 on their GigabitEthernet0/0 interfaces. The engineer checks the OSPFv3 neighbor status on R1 and sees that the neighbor state is stuck in EXSTART. The engineer verifies that both interfaces are up and have IPv6 link-local addresses. What is the most likely cause of this problem?

A.Configure a global unicast IPv6 address on the interface.

B.Ensure that the MTU is the same on both sides of the link.

C.Change the router ID to be the same on both routers.

D.Change the network type to point-to-point.

AnswerB

An MTU mismatch prevents OSPFv3 from completing the DBD packet exchange, leaving the neighbor state stuck in EXSTART. During this phase, routers send Database Description packets that must fit within the interface MTU; if one side's MTU is lower, the packets are dropped, and the routers keep retransmitting without progressing to EXCHANGE. Aligning the MTU on both ends allows the DBD exchange to complete, moving the adjacency to FULL.

Why this answer

The EXSTART state in OSPF indicates that the routers have formed a bidirectional communication and are negotiating the master/slave relationship and the initial Database Description (DBD) packet exchange. A common cause for getting stuck in EXSTART is an MTU mismatch between the two interfaces, which prevents the DBD packets from being accepted by the neighbor, causing the process to stall.

Exam trap

Cisco often tests the MTU mismatch as a specific cause for OSPF adjacency being stuck in EXSTART, and candidates may mistakenly focus on router IDs or addressing instead of the packet size negotiation.

Why the other options are wrong

The problem is not due to missing global addresses; the adjacency is stuck at EXSTART, not at DOWN or INIT.

The show output shows different router IDs (192.168.1.1 and 192.168.1.2), so this is not the issue.

The adjacency is stuck in EXSTART, which is not typically resolved by changing network type; the issue is related to packet exchange.

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261

MCQhard

A packet is destined for 192.168.40.130. The routing table contains 192.168.40.0/24, 192.168.40.128/25, and 0.0.0.0/0. Which route is used?

A.192.168.40.0/24

B.192.168.40.128/25

C.0.0.0.0/0

D.No route can be used because the entries overlap

AnswerB

The /25 prefix is the longest match for 192.168.40.130, since that address falls within the 192.168.40.128–192.168.40.255 range. Longest-prefix match governs route selection, so this entry beats both the /24 covering 192.168.40.0–192.168.40.255 and the default route.

Why this answer

The /25 route is used because it is the most specific matching prefix. In plain language, even though the /24 and the default route also technically match, the router prefers the entry that most precisely describes the destination range. Since 192.168.40.130 falls inside 192.168.40.128/25, that route wins under longest-prefix match.

This is a classic routing-table interpretation pattern. The router does not start with the default route when more specific routes exist, and it does not choose the /24 simply because it is familiar. Specificity comes first.

Exam trap

A common exam trap is assuming that the default route or a larger subnet like /24 will be chosen over a more specific subnet like /25. Candidates may incorrectly think the default route is preferred or that overlapping routes cause ambiguity. However, routers always use the longest prefix match rule, which means the route with the most specific subnet mask that includes the destination IP is selected.

Misunderstanding subnet mask lengths or ignoring longest prefix match leads to wrong answers in routing questions.

Why the other options are wrong

192.168.40.0/24 is a valid route but less specific than 192.168.40.128/25. Since the destination IP falls within both, the router prefers the more specific /25 route, so this option is incorrect.

0.0.0.0/0 is the default route and only used when no other route matches. Since more specific routes exist for the destination IP, this option is incorrect.

Overlapping routes like /24 and /25 are common and resolved by longest prefix match. The presence of overlapping entries does not prevent route selection, so this option is incorrect.

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262

MCQhard

Two OSPF routers connected over Ethernet fail to become neighbors. Their interfaces are up/up and in the same IPv4 subnet. One router uses area 0 and the other uses area 1 on the connecting interfaces. What is the most likely cause?

A.Mismatched OSPF process IDs

B.Mismatched OSPF areas on the shared link

C.Missing default routes

D.Different router IDs

AnswerB

OSPF neighbors must agree on the area ID configured on the link. If one router places the interface in area 0 and the other in area 1, Hello packets are rejected because the area ID field doesn't match, preventing neighbor state from advancing beyond INIT. This is a fundamental adjacency requirement, separate from process ID or router ID issues.

Why this answer

OSPF neighbors on the same link must agree on key parameters, including the area assigned to that interface. A mismatch prevents the adjacency from forming.

Exam trap

A common exam trap is assuming that OSPF process IDs must match between neighbors for adjacency to form. Many candidates mistakenly focus on process ID alignment, but OSPF process IDs are locally significant and do not need to match. The real cause of adjacency failure in this scenario is the mismatch in OSPF area IDs on the shared link.

This subtle difference often leads to confusion, causing candidates to overlook the critical role of area consistency in neighbor formation and select incorrect answers related to process IDs or router IDs.

Why the other options are wrong

Mismatched OSPF process IDs do not prevent neighbor formation because process IDs are locally significant identifiers on each router. They do not need to match for adjacency to form, so this option is incorrect.

Missing default routes do not affect OSPF neighbor formation. Default routes influence routing decisions but are not required for establishing OSPF adjacencies, so this option is incorrect.

Different router IDs are necessary for OSPF neighbors to uniquely identify each router. Having different router IDs does not cause adjacency failure, so this option is incorrect.

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263

MCQhard

An administrator configures a GRE tunnel interface on a router with the following: interface Tunnel0, tunnel source GigabitEthernet0/0, tunnel destination 192.168.2.2. What is the main purpose of this configured tunnel?

A.It creates a logical tunnel across another network.

B.It enables PPP authentication on a serial interface.

C.It configures WPA3 security for a wireless bridge.

D.It enables BGP between autonomous systems automatically.

AnswerA

The configured tunnel interface takes the original packet and wraps it in a new IP header, with the tunnel source and destination addresses serving as the endpoints of that encapsulation. This creates a logical, virtual path that traverses an underlying physical or routed network, allowing traffic from two remote sites to appear as if they are directly connected even though they are separated by intermediate hops. Thus, the purpose is to establish an overlay network across another network, not to provide any security or link-level protocol function.

Why this answer

GRE is a tunneling mechanism used to carry one type of traffic over another network path by encapsulating packets. In practical terms, the configuration creates a logical tunnel between endpoints so traffic can cross an underlying IP network as if a virtual path existed between them. The key point is that GRE is about tunneling, not encryption by itself.

This distinction matters because people often assume tunnels automatically imply encryption. GRE by itself does not provide that.

Exam trap

A frequent exam trap is confusing GRE tunnels with encryption or automatic routing protocol establishment. Candidates often assume that because GRE creates a tunnel, it also encrypts traffic or automatically enables protocols like BGP. However, GRE only encapsulates packets and does not provide confidentiality or integrity.

Encryption requires pairing GRE with IPsec. Additionally, routing protocols must be explicitly configured over the tunnel interface; the tunnel itself does not initiate or enable them. Misreading the tunnel configuration as PPP authentication or wireless security is another common pitfall, as GRE operates at Layer 3 and is unrelated to those technologies.

Why the other options are wrong

Incorrect. PPP authentication applies to serial interfaces and point-to-point links, but the exhibit shows a GRE tunnel configuration, not PPP on a serial link.

Incorrect. WPA3 is a wireless security protocol unrelated to GRE tunnels, which operate at Layer 3 and do not configure wireless security settings.

Incorrect. GRE tunnels do not automatically enable BGP or any routing protocol; routing protocols must be explicitly configured over the tunnel interface.

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264

Drag & Dropmedium

Drag and drop the following OSPFv2 neighbor state transitions into the correct order, starting from the initial state when no neighbor information has been received.

Drag or tap steps into the slots.

Steps

Order

1Step 1

2Step 2

3Step 3

4Step 4

Why this order

OSPF neighbor states begin at Down, then Init after receiving Hello, 2-Way after seeing own router ID, ExStart for master/slave negotiation, and Exchange for exchanging database descriptors.

Exam trap

Do not confuse the order of ExStart and Exchange; ExStart always precedes Exchange. Also, remember that 2-Way comes after Init, not before.

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265

MCQhard

Why is traffic to 10.10.10.200 using the EIGRP route instead of the OSPF route, given that both routes have the same prefix length?

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

B.Because OSPF routes are never installed when EIGRP is present.

C.Because OSPF can be used only for IPv6 routes.

D.Because EIGRP routes always have a smaller subnet mask than OSPF routes.

AnswerA

Both EIGRP and OSPF have learned routes to 10.10.10.0/24, so the prefix lengths are identical, meaning longest-match selection does not break the tie. Cisco's default administrative distance for internal EIGRP is 90, while OSPF's is 110; since lower AD is preferred, the EIGRP route is installed in the routing table. This is the correct explanation of why traffic to 10.10.10.200 uses the EIGRP path.

Why this answer

When two routes have the same prefix length, the router uses administrative distance to choose the route with the lowest value. EIGRP has a default administrative distance of 90, while OSPF uses 110. Therefore, the EIGRP route is preferred.

Exam trap

A common mistake is to assume that OSPF routes always have a lower administrative distance than EIGRP routes.

Why the other options are wrong

OSPF routes are installed when EIGRP is present; routing protocols coexist and the route with the lowest AD is selected.

OSPF supports both IPv4 and IPv6; it is not limited to IPv6.

EIGRP routes do not always have a smaller subnet mask; prefix length is determined by the network design, not the routing protocol.

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266

Multi-Selectmedium

Which TWO statements about IPv4/IPv6 static routing are true?

Select 2 answers

A.A floating static route is configured with a lower administrative distance than the primary route.

B.An IPv6 default static route can be configured using the destination prefix ::/0.

C.A static route with an administrative distance of 1 is preferred over a directly connected route.

D.A floating static route becomes active in the routing table only when the primary route is removed or fails.

E.IPv4 and IPv6 static routes are configured using the same command syntax.

AnswersB, D

The IPv6 default static route uses the destination prefix ::/0, which matches any IPv6 address, analogous to IPv4's 0.0.0.0/0. It is commonly configured with the command 'ipv6 route ::/0' followed by a next-hop address or exit interface. This allows the router to forward all unmatched IPv6 traffic to a designated gateway.

Why this answer

The IPv6 default static route uses the destination prefix ::/0, which matches all IPv6 addresses, similar to 0.0.0.0/0 in IPv4. Option D is correct because a floating static route is configured with a higher administrative distance and only becomes active when the primary route (with a lower AD) is removed or fails. Option A is wrong: a floating static route is configured with a higher administrative distance, not lower.

Option C is wrong: a directly connected route has an administrative distance of 0, which is always preferred over a static route (even with AD 1). Option E is wrong: IPv4 static routes use the 'ip route' command, while IPv6 static routes use the 'ipv6 route' command; the syntax is different.

Exam trap

Cisco often tests the inverse relationship between administrative distance and route preference, trapping candidates who think a lower AD makes a route less preferred rather than more preferred.

Why the other options are wrong

A floating static route is configured with a higher administrative distance than the primary route, not lower.

A directly connected route has an administrative distance of 0, which is preferred over a static route with AD 1.

IPv4 static routes use the 'ip route' command, while IPv6 static routes use the 'ipv6 route' command; the syntax is different.

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267

MCQhard

Based on the exhibit, what is the most likely reason the PPP link is failing to authenticate?

A.The PPP authentication credentials do not match between the two sides.

B.The interfaces must use HDLC instead of PPP before authentication can work.

C.CHAP requires the routers to be in different IPv4 subnets.

D.PPP authentication works only over GRE tunnels.

AnswerA

CHAP authentication relies on a shared secret that must be identical on both routers. The exhibit shows the CHAP password configured on one side is different from the other, so the hash computed during the challenge-response handshake will not match and the PPP link will fail authentication. Without matching credentials, the link cannot transition to the established state.

Why this answer

The most likely reason is a credentials mismatch between the two sides of the PPP authentication setup. In practical terms, PPP authentication requires the peers to agree on the relevant identity and secret information. If those values do not align, the link may come up physically but authentication fails and the logical connection does not establish properly.

This is a very exam-relevant WAN troubleshooting scenario because it focuses on a realistic failure after the transport is already present.

Exam trap

Be careful not to confuse physical link issues with authentication problems. Just because the link is up doesn't mean authentication is successful.

Why the other options are wrong

This option is incorrect because PPP (Point-to-Point Protocol) does not require HDLC (High-Level Data Link Control) for authentication; PPP can authenticate independently of the encapsulation method used.

This option is incorrect because CHAP (Challenge Handshake Authentication Protocol) does not require routers to be in different IPv4 subnets for authentication to function. CHAP can authenticate devices regardless of their subnet configuration as long as they can reach each other over the network.

This option is incorrect because PPP (Point-to-Point Protocol) can operate independently of GRE (Generic Routing Encapsulation) tunnels; authentication can occur directly over a PPP link without requiring GRE.

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268

MCQhard

A router has the following routes in its table: 172.16.0.0/16, 172.16.20.0/24, and 172.16.20.128/25. Which route is used for traffic to 172.16.20.200?

A.172.16.0.0/16

B.172.16.20.0/24

C.172.16.20.128/25

D.The default route

AnswerC

The destination IP 172.16.20.200 falls within the subnet 172.16.20.128/25 (range 172.16.20.128 to 172.16.20.255). According to the longest prefix match rule, this route has a prefix length of 25, which is longer (more specific) than the other candidate routes (default /0 and 172.16.0.0/16 /16), so it is preferred. The route 172.16.20.0/24 also matches but is less specific because /24 is shorter than /25. Thus, the router forwards the packet using the /25 route.

Why this answer

The /25 route is used because it is the most specific match. In plain language, the router looks for the narrowest route that still contains the destination address. Since 172.16.20.200 falls inside 172.16.20.128/25, that route wins over the broader /24 and /16 entries.

This is a direct longest-prefix-match question. It is meant to reinforce that specificity comes first in routing-table lookup. Broader routes remain useful, but they are not chosen when a more precise matching entry exists.

Exam trap

A frequent exam trap is selecting a broader subnet route such as 172.16.20.0/24 or 172.16.0.0/16 instead of the more specific 172.16.20.128/25. Candidates may mistakenly believe that any matching route is acceptable or that larger subnets are preferred. This misunderstanding ignores the fundamental longest prefix match rule used by Cisco routers, which always prioritizes the most specific route.

Falling for this trap leads to incorrect routing decisions and exam errors.

Why the other options are wrong

172.16.0.0/16 is the least specific route covering a large address range. Although it matches the destination IP, it is overridden by more specific routes with longer subnet masks, so it is not used.

172.16.20.0/24 is more specific than the /16 but less specific than the /25 route. Since the destination IP falls within the /25 subnet, the router prefers the /25 route over this /24.

The default route is only used when no other routes match the destination IP. Since multiple specific routes exist that match the destination, the default route is not selected.

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269

MCQhard

A router has a directly connected route to 10.1.1.0/24 and a static default route. Which route is used for traffic to 10.1.1.200?

A.The directly connected 10.1.1.0/24 route

B.The static default route

C.Both routes equally

D.Neither route

AnswerA

The directly connected 10.1.1.0/24 route is selected because routers perform a longest prefix match when forwarding packets. The destination 10.1.1.1 falls within the 10.1.1.0/24 subnet, which has a 24-bit prefix, making it more specific than any default route. Since the connected route is present in the routing table, it takes precedence over less specific routes.

Why this answer

The directly connected route is used because it is the most specific and most immediate match. In practical terms, the router already knows that 10.1.1.200 belongs to a network on one of its own interfaces, so there is no reason to use the default route. The default route exists only for destinations that do not match anything more specific.

This is one of the most fundamental route-selection behaviors in IP routing.

Exam trap

A frequent exam trap is selecting the static default route for traffic destined to an IP address within a directly connected subnet. Candidates might incorrectly believe the default route overrides connected routes due to its static configuration or because it is manually set. However, the router always prefers the most specific route, which is the directly connected subnet in this case.

Misunderstanding the longest prefix match and administrative distance hierarchy leads to this error. Remember, the default route is only a fallback when no other route matches the destination IP address.

Why the other options are wrong

This option is incorrect because the static default route is less specific (0.0.0.0/0) and only used when no other route matches the destination. Since a connected route exists, the default route is ignored.

This option is wrong because routing does not load balance between a directly connected route and a static default route. The router selects the single best route based on prefix length and administrative distance.

This option is incorrect because the router clearly has a matching directly connected route for 10.1.1.200. Therefore, it will use that route rather than discarding both or failing to forward.

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270

PBQhard

You are connected to R1 via the console. R1 is a newly deployed router that connects two subnets: 192.168.1.0/24 on GigabitEthernet0/0 and 192.168.2.0/24 on GigabitEthernet0/1. There is a default route to the Internet via ISP router at 203.0.113.1, but the network policy requires that traffic from 192.168.1.0/24 to the Internet must exit via a different next-hop 203.0.113.2. You need to implement policy-based routing on R1 to forward traffic from source 192.168.1.0/24 to 203.0.113.2, while all other traffic uses the default route via 203.0.113.1.

Hints

•Policy-based routing uses route-maps applied to incoming interfaces.
•The route-map matches traffic using an access list and sets the next-hop.
•Verify the route-map and its application on the correct interface.

A.Create an access list matching source 192.168.1.0/24, a route-map with set ip next-hop 203.0.113.2, and apply the route-map inbound on GigabitEthernet0/0.

B.Create an access list matching source 192.168.1.0/24, a route-map with set ip next-hop 203.0.113.2, and apply the route-map outbound on GigabitEthernet0/1.

C.Create an access list matching destination 203.0.113.2, a route-map with set ip next-hop 203.0.113.2, and apply the route-map inbound on GigabitEthernet0/0.

D.Configure a static route for 192.168.1.0/24 with next-hop 203.0.113.2 and rely on the default route for other traffic.

AnswerA

solution

! R1
access-list 101 permit ip 192.168.1.0 0.0.0.255 any
route-map PBR permit 10
match ip address 101
set ip next-hop 203.0.113.2
interface GigabitEthernet0/0
ip policy route-map PBR

Why this answer

Policy-based routing (PBR) on Cisco IOS is implemented using route-maps that are applied to an interface to override the normal destination-based forwarding decision. The correct approach is to match the source subnet 192.168.1.0/24 with an ACL, then use a route-map with 'set ip next-hop 203.0.113.2', and apply it inbound on the interface where the traffic enters the router (GigabitEthernet0/0). Applying it inbound ensures that packets from that subnet are policy-routed before the routing table lookup, so they exit via the specified next-hop while all other traffic follows the default route.

Exam trap

The trap here is confusing the direction of policy application: candidates often think PBR should be applied outbound on the exit interface or that matching the destination is sufficient, but PBR must be applied inbound on the ingress interface and match the source to enforce source-based forwarding.

Why the other options are wrong

PBR must be applied inbound on the interface receiving the traffic, not outbound on the exit interface.

PBR uses the access list to match traffic based on source, destination, or other criteria; here the requirement is to match source subnet.

A static route controls forwarding based on destination, not source. Policy-based routing is needed to forward based on source address.

271

MCQhard

Refer to the exhibit. A network engineer is verifying OSPF routing on R1. All routers in the topology are expected to reside in OSPF area 0, and the network 172.16.0.0/16 should be advertised from R2 within the same area. The engineer issues the show ip route 172.16.0.0 command on R1 and sees the output in the exhibit. The engineer expected to see an intra-area route (O) instead of an inter-area route (O IA). What is the most likely cause of this discrepancy?

A.R1 has a mismatched OSPF process ID compared to the ABR.

B.The network type on GigabitEthernet0/0 is configured as non-broadcast, preventing full adjacency.

C.The metric for the route is too high, causing OSPF to treat it as an inter-area route.

D.The destination network 172.16.0.0/16 is located in a different OSPF area.

AnswerD

The routing table entry shows 'type inter area'. This indicates the prefix is being learned via an OSPF Type-3 summary LSA, which is only generated when the network is in a different area than the local router. Therefore, the network is indeed in a different area, contradicting the assumption that R1 and the destination are both in area 0.

Why this answer

The route 172.16.0.0/16 appears as O IA (inter-area) on R1, which means R1 learned it via a Type 3 LSA from an ABR. For the route to be intra-area (O), the destination network must reside in the same OSPF area (area 0) as R1. Since R2 is advertising this network, if it were truly in area 0, R1 would see an O route.

The O IA designation indicates that the network is in a different area, likely because R2's interface connected to 172.16.0.0/16 is configured in a different OSPF area, or R2 is acting as an ABR.

Exam trap

Cisco often tests the distinction between intra-area and inter-area OSPF routes, and the trap here is that candidates mistakenly think a high metric or mismatched process ID can change the route type, when in fact only the area configuration determines whether a route is O or O IA.

Why the other options are wrong

Candidates mistakenly assume that OSPF process IDs must match globally for proper LSA exchange, but they are only locally significant.

Candidates may think that the network type influences the OSPF LSA type, but it only affects neighbor discovery and DR/BDR election, not the area origin of LSAs.

Candidates sometimes confuse the metric influence with the route type, thinking that OSPF converts routes when the cost exceeds a threshold.

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272

MCQhard

R1 and R2 are connected via a shared Ethernet segment. Both routers are configured in OSPF area 0 and are on the same IP subnet. OSPF authentication is enabled on both interfaces, but the adjacency is not forming. What is the most likely reason?

A.The OSPF authentication key does not match on the two routers.

B.The routers must use different OSPF areas to become neighbors.

C.OSPF message-digest authentication can be used only on serial links.

D.The routers must remove IP addressing before OSPF can form.

AnswerA

OSPF interfaces configured with an authentication key must match the key and key ID on neighboring routers. When R1 sends a Hello packet, it computes an authentication hash using its configured key; R2 verifies that value with its own key. A mismatch causes the receiving router to silently drop the Hello, so no adjacency can form even though all other OSPF parameters are correct.

Why this answer

The most likely reason is an OSPF authentication mismatch. In practical terms, both routers are on the same IP subnet and in the same area, but they are not using the same authentication key on the shared link. OSPF neighbors must agree on key authentication parameters before they will trust each other enough to form an adjacency.

This is a classic CCNA troubleshooting pattern because the configuration looks almost correct until you compare the security settings carefully.

Exam trap

A frequent exam trap is selecting an answer that incorrectly states OSPF authentication is limited to serial links or that routers must be in different areas to form adjacency. Candidates may also mistakenly believe that removing IP addressing is necessary for OSPF to form. These misconceptions overlook that OSPF authentication applies to Ethernet interfaces and that neighbors must be in the same area and subnet with matching authentication keys.

Misreading these details leads to choosing incorrect options that seem plausible but contradict OSPF adjacency rules.

Why the other options are wrong

This option is incorrect because OSPF neighbors must be in the same area to form adjacency. Using different areas on the same segment prevents adjacency, so this option contradicts OSPF area rules.

This option is incorrect because OSPF authentication, including message-digest (MD5), is supported on Ethernet interfaces, not just serial links. Authentication is not limited by interface type.

This option is incorrect because OSPF requires valid IP addressing on interfaces to operate. Removing IP addressing disables OSPF on that link, so adjacency cannot form without IP addresses.

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273

MCQmedium

R3 has the static route 'ip route 172.20.8.0 255.255.255.0 192.168.1.1'. Packets destined for 172.20.8.0/24 are being dropped. What is the most likely cause?

A.The destination network mask should be /16 instead of /24

B.The next-hop address is not reachable from R3

C.Static routes require an outbound access list

D.The route must use administrative distance 255

AnswerB

The static route is invalid because R3 cannot resolve the specified next-hop address. A static route with a next-hop IP requires that the next-hop be reachable via a directly connected network or another valid route in the routing table; otherwise, the route is not installed. Since the next-hop is unreachable, packets cannot be forwarded and the route remains inactive.

Why this answer

A static route can only work if the next-hop address is reachable. If the next hop is down or missing from the routing table, the route cannot forward traffic successfully.

Exam trap

A frequent exam trap is assuming that an incorrect subnet mask on the static route causes packets to be dropped. While subnet masks affect routing accuracy, they do not cause next-hop reachability failures. Another trap is believing that static routes require outbound ACLs, which is false; ACLs control traffic filtering but do not impact static route functionality.

Additionally, some may think setting the administrative distance to 255 is necessary for static routes, but this actually disables the route, making it unusable. The key mistake is overlooking the requirement that the next-hop IP address must be reachable for the static route to work, which is the actual cause of packet drops in this scenario.

Why the other options are wrong

Option A suggests changing the destination network mask from /24 to /16. While subnet masks must be correct for proper routing, an incorrect mask does not cause next-hop reachability issues or packet drops due to unreachable next-hop addresses. The problem here is related to next-hop reachability, not the destination mask.

Option C incorrectly states that static routes require an outbound access list. Static routes do not need ACLs to function; ACLs are used for traffic filtering and security policies, not for enabling or disabling static routes. This option is invalid.

Option D claims the route must use administrative distance 255. Administrative distance 255 actually makes a route unusable, so setting it to 255 would prevent the static route from working. The default administrative distance for static routes is 1, which is preferred over most dynamic routes.

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274

MCQmedium

What is an autonomous system in basic BGP terminology?

A.A collection of networks and routers under common administrative routing control

B.A single switch VLAN

C.A specific OSPF area inside one router

D.A type of wireless access point

AnswerA

In BGP terminology, an autonomous system (AS) is a set of routers and networks that operate under a single administrative domain and present a consistent routing policy to other ASes. It is identified by a globally unique AS number (ASN) and exchanges reachability information with external peers via BGP, making it the fundamental unit of inter-domain routing.

Why this answer

An autonomous system is a collection of IP networks and routers under a common routing policy or administrative control. In practical terms, it is the domain boundary concept used in BGP discussions. BGP uses AS concepts to reason about routing between separate administrative networks.

This is one of the first BGP ideas learners need to understand.

Exam trap

A frequent exam trap is mistaking an autonomous system for a VLAN or an OSPF area. VLANs are Layer 2 broadcast domains and do not relate to routing domains or administrative control of routing policies. Similarly, OSPF areas segment a single routing domain to optimize routing but do not represent separate administrative entities.

Confusing these concepts can lead to incorrect answers because BGP’s autonomous system concept specifically refers to a collection of networks and routers under a common administrative routing policy, which is distinct from VLAN or OSPF area segmentation.

Why the other options are wrong

This option is incorrect because a VLAN is a Layer 2 segmentation method that isolates broadcast domains and does not relate to routing policies or autonomous systems in BGP.

This option is wrong since an OSPF area is a subdivision within a single routing domain to optimize routing, not an autonomous system representing separate administrative control.

This option is incorrect because an autonomous system is a routing domain concept, whereas a wireless access point is a physical device unrelated to BGP or routing domains.

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275

Drag & Dropmedium

Drag and drop the following steps into the correct order to configure HSRP on an interface and verify the active/standby election process, including failover and verification.

Drag or tap steps into the slots.

Steps

Order

1Step 1

2Step 2

3Step 3

4Step 4

Why this order

Only option A correctly orders the steps for configuring HSRP on an interface. The proper sequence is: enter interface configuration mode, set the HSRP version, configure the virtual IP, set priority if needed, enable preempt, and verify with 'show standby'. Options B, C, and D contain incorrect steps or order.

B suggests creating a VLAN and assigning an IP to the VLAN interface, which is not part of HSRP configuration (HSRP is configured on an existing Layer 3 interface, not by creating a VLAN). C places priority before virtual IP and uses 'show running-config' for verification, which does not show active/standby roles. D incorrectly assumes HSRP is enabled globally and uses 'debug standby' for initial verification, which is not the standard first verification command.

Exam trap

Candidates often confuse the order of HSRP configuration steps or think HSRP requires a global configuration mode like routing protocols. Remember: HSRP is configured per interface, and verification uses 'show standby' to see real-time roles.

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276

Drag & Dropmedium

Drag and drop the following OSPFv2 neighbor state transitions and DR/BDR election steps into the correct order for a multi-access network where a new router joins an existing OSPF area.

Drag or tap steps into the slots.

Steps

Order

1Step 1

2Step 2

3Step 3

4Step 4

Why this order

The new router first discovers neighbors via Hello. Then DD, LSR, LSU exchange synchronizes databases. DR/BDR election happens before Full state is achieved.

Exam trap

Do not confuse the order of ExStart and Exchange, or Loading and Full. Remember that DR/BDR election occurs after 2-Way and before ExStart.

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277

MCQmedium

A network engineer enters the following configuration on R1 and R2, but R1 cannot form an OSPF adjacency with R2 on interface GigabitEthernet0/0. R1# show running-config interface GigabitEthernet0/0 interface GigabitEthernet0/0 ip address 10.0.0.1 255.255.255.0 ip ospf hello-interval 10 ip ospf dead-interval 40 ip ospf 1 area 0 ! R2# show running-config interface GigabitEthernet0/0 interface GigabitEthernet0/0 ip address 10.0.0.2 255.255.255.0 ip ospf hello-interval 5 ip ospf dead-interval 20 ip ospf 1 area 0 What is the most likely cause of the failure?

A.The routers are in different OSPF areas.

B.The OSPF timers on the interface do not match.

C.The subnet mask prevents multicast OSPF packets from being exchanged.

D.The OSPF process IDs do not match on the two routers.

AnswerB

This is correct because the interfaces are configured with different hello and dead intervals. OSPF neighbors expect those timers to align, and if they do not, the routers reject the neighbor relationship. The addressing and area assignment are fine, but the timer mismatch blocks adjacency formation.

Why this answer

The routers must agree on hello and dead timers to establish an OSPF adjacency. R1 uses hello=10 and dead=40, while R2 uses hello=5 and dead=20; this mismatch prevents the neighbor relationship. Although both routers share the same area (0) and subnet mask, and OSPF process IDs are locally significant (no match required), the timer difference is the root cause.

Exam trap

Remember that OSPF process IDs are locally significant and do not need to match between routers.

Why the other options are wrong

This option is incorrect because OSPF can still form adjacencies between routers in different areas, provided they are correctly configured to do so. The issue in this scenario is related to OSPF timers, not area mismatches.

This option is incorrect because OSPF can still exchange multicast packets even if the subnet mask is not configured correctly, as long as the interfaces are up and configured for OSPF. The failure to form an adjacency is more likely due to mismatched OSPF timers.

This option is wrong because OSPF process IDs do not need to match for routers to form an adjacency; they only need to be in the same area and have matching network statements.

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278

MCQhard

An administrator has just configured OSPF in a single area between router R1 and router R2, which are directly connected via their Gi0/0 interfaces with IP addresses 10.0.0.1/30 and 10.0.0.2/30. On R1, the command show ip ospf neighbor shows no entries, and a further check on R2 with show ip ospf interface gi0/0 indicates that the interface is passive. Which configuration error is most likely causing the adjacency failure?

A.The network command on R1 does not cover the 10.0.0.0/30 subnet.

B.R2 has the passive-interface default command but no no passive-interface command for Gi0/0.

C.The OSPF process IDs on R1 and R2 are mismatched.

D.The hello and dead intervals on R1 and R2 are not the same.

AnswerB

The passive-interface default command sets all OSPF interfaces to passive mode. To allow neighbor adjacency on a specific interface, a no passive-interface <interface> command is required. Without it, Gi0/0 remains passive, preventing OSPF hellos and adjacency formation.

Why this answer

The output on R2 shows the Gi0/0 interface is passive, meaning OSPF will not send or receive hello packets on that interface, preventing neighbor discovery. The passive-interface default command makes all interfaces passive by default, and without a no passive-interface Gi0/0 command, the interface remains passive, blocking adjacency formation. This directly explains why R1's show ip ospf neighbor shows no entries.

Exam trap

Cisco often tests the distinction between passive-interface default and the need for explicit no passive-interface commands, as candidates may assume that OSPF will automatically form adjacencies on directly connected interfaces without considering passive configuration.

Why the other options are wrong

This option fails to account for the explicit passive interface state shown on R2. A missing network statement would not cause the interface to be displayed as passive; it would simply not be enrolled in the OSPF process.

This is a common misconception, but process ID mismatch does not affect OSPF neighbor formation. The passive interface status on R2 directly contradicts this as the cause.

The passive interface status would not appear if the only issue were interval mismatches; the interface would still be active and sending hellos. This directly conflicts with the given show output.

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279

MCQhard

After configuring the area 0 range 10.0.0.0 255.255.0.0 command on an OSPF ABR, a technician finds that a host at 10.0.5.100 in Area 1 cannot reach hosts in Area 0. The ABR’s OSPF database shows only the summary 10.0.0.0/16 in Area 0, and no individual /24 routes. What is the most likely cause?

A.The ABR is filtering the specific /24 routes using a distribute-list under the OSPF process.

B.The routers in Area 1 are no longer advertising their /24 routes to the ABR because the ABR is in a different area.

C.The area range command causes the ABR to advertise only the summary LSA and suppress the more-specific Type-3 LSAs for the range.

D.The ABR has automatically created a discard route to null0 for the summary, which is dropping all traffic destined to the summarized networks.

AnswerC

By default, the area range command summarizes the specified prefix range and suppresses the individual component routes from being advertised into the target area. Only the summary LSA appears in Area 0, which matches the observed behavior.

Why this answer

The `area 0 range 10.0.0.0 255.255.0.0` command on an OSPF ABR creates a single Type-3 summary LSA (10.0.0.0/16) for Area 0 and suppresses the advertisement of more-specific Type-3 LSAs (e.g., /24 routes) that fall within that range. This is the intended behavior of the `range` command: it summarizes routes at the ABR and prevents the individual component routes from being advertised into the backbone area. Since the host at 10.0.5.100 in Area 1 relies on those specific /24 routes to reach destinations in Area 0, the suppression breaks connectivity.

Exam trap

Cisco often tests the misconception that the `area range` command only summarizes routes without suppressing the more-specific LSAs, leading candidates to incorrectly attribute the connectivity loss to filtering or routing issues rather than the intended suppression behavior.

Why the other options are wrong

A distribute-list requires explicit configuration; its absence makes this an unsubstantiated guess.

Area border routers receive all LSAs from non-backbone areas; the area boundary does not stop LSA propagation to the ABR itself.

The null0 route is a loop-prevention mechanism, not an absolute traffic blocker; more-specific entries in the routing table take precedence.

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280

MCQhard

A technician is troubleshooting an OSPF network. On a broadcast segment, R1 is the DR and R2 is the BDR. R1's interface GigabitEthernet0/0 is shut down for maintenance. The technician expects that R2 will assume the DR role, but instead a new DR election occurs and another router is elected DR. What is the most likely cause?

A.The OSPF hello and dead intervals on R2 do not match those of other routers on the segment.

B.R2 has an OSPF priority of 255.

C.The OSPF network type on the segment was changed to point-to-point.

D.R2 has an OSPF priority of 0.

AnswerD

On a broadcast OSPF network, a priority of 0 makes a router ineligible for DR or BDR election. Even though R2 was the BDR, its priority of 0 prevents it from taking over as DR when R1 fails. Consequently, a new DR election is triggered among the remaining eligible routers, and a router other than R2 becomes the new DR.

Why this answer

When the DR (R1) goes down, a new DR election occurs. R2 is the BDR, but if its OSPF priority is 0, it is ineligible to become the DR. Therefore, a new election takes place among the remaining routers with non-zero priorities, and another router wins the DR role.

Exam trap

Cisco often tests the misconception that the BDR automatically becomes DR when the DR fails, but the BDR only takes over if it has a non-zero priority; otherwise, a new election is triggered.

Why the other options are wrong

Neighbor adjacency failure due to timer mismatch would have prevented R2 from becoming BDR at all.

High priority increases the chance of being elected DR, not decrease it.

Point-to-point networks do not have DR/BDR elections, so R2 could not have been BDR.

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281

Drag & Dropmedium

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

Drag or tap steps into the slots.

Steps

Order

1Step 1

2Step 2

3Step 3

4Step 4

Why this order

The correct sequence for configuring OSPFv3 on a Cisco IOS-XE router is: first enable IPv6 routing globally with `ipv6 unicast-routing` (A), then create the OSPFv3 process with `router ospfv3 1` (B), then enter interface configuration mode for the desired interface with `interface GigabitEthernet0/0` (C), and finally enable OSPFv3 on that interface using `ipv6 ospf 1 area 0` (D). This order ensures IPv6 is enabled before configuring OSPFv3, the OSPFv3 process exists before it is assigned to an interface, and the interface is selected before applying the OSPFv3 configuration.

Exam trap

Do not confuse the order with OSPFv2. For OSPFv3, you must first enable IPv6 routing globally; otherwise, the router will reject OSPFv3 configuration commands.

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282

MCQhard

R1 and R2 are directly connected via Ethernet on interface G0/0. Both interfaces are in the same subnet and configured for OSPF area 0. After enabling OSPF, R1's G0/0 is stuck in the INIT state in the OSPF neighbor table. What is the most likely cause?

A.MTU mismatch

B.Hello and dead timer mismatch

C.Missing router ID on both routers

D.A duplicate static route to 10.1.12.0/30

AnswerB

OSPF adjacency requires that Hello and Dead intervals match exactly between neighbors on the same link. The Dead interval is typically four times the Hello interval, but if one side is configured with different timers (e.g., 10/40 vs 30/120), the routers will discard each other's Hello packets and never reach the 2-Way state. This is the classic cause of a neighbor relationship that remains completely down, with no OSPF neighbor entry at all.

Why this answer

Being stuck in the INIT state means R1 has received Hello packets from R2 but has not transitioned to the 2-WAY state. This most often occurs when critical OSPF parameters like the hello and dead timers do not match. An MTU mismatch, while problematic, would cause the adjacency to fail during database exchange (Exstart/Exchange), not during initial neighbor formation.

Missing router IDs are not a real issue because routers auto-generate them, and a duplicate static route to the connected subnet would not affect OSPF neighbor discovery.

Exam trap

A common exam trap is selecting MTU mismatch or missing router IDs as the cause of OSPF adjacency failure. While MTU mismatches can cause adjacency issues during database exchange, they do not prevent the initial neighbor relationship from forming. Missing router IDs do not block adjacency because routers automatically generate IDs if none are configured.

Another trap is confusing static routes with neighbor discovery; static routes do not influence OSPF adjacency. The key is to focus on timer mismatches, as hello and dead intervals must be identical for routers to recognize each other as neighbors and establish adjacency.

Why the other options are wrong

MTU mismatch can cause OSPF adjacency problems during the database exchange phase, but it does not typically prevent the initial neighbor relationship from forming. Since the question states adjacency cannot form, MTU mismatch is unlikely the primary cause.

Missing router IDs do not prevent OSPF adjacency because routers automatically generate a router ID if none is configured. Therefore, this option is not a valid cause for adjacency failure.

A duplicate static route to 10.1.12.0/30 does not affect OSPF neighbor formation, as static routes are unrelated to OSPF adjacency processes. This option is irrelevant to the adjacency issue.

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283

MCQhard

A router has a static route configured: ip route 10.200.0.0 255.255.0.0 GigabitEthernet0/1. The output of show ip interface brief shows that interface GigabitEthernet0/1 is administratively down. Why is the route to 10.200.0.0/16 present in the running configuration but absent from the routing table?

A.Because the route points to an interface that is administratively down.

B.Because static routes cannot reference exit interfaces.

C.Because the destination must be a /24, not a /16.

D.Because static routes require NTP before installation.

AnswerA

A static route that specifies only an exit interface is installed in the routing table only when that interface is in an up/up state. An administratively down interface (shutdown) makes the route invalid because the router cannot use that path for packet forwarding, even though the configuration exists. Therefore the route is absent from the show ip route output and no traffic is sent to 10.200.0.0/16.

Why this answer

The static route is absent because the outgoing interface is down. In practical terms, when a static route depends on an interface that is not operational, the router cannot use that path, so the route is not installed as usable forwarding state. The configuration line alone is not enough; the forwarding path also has to be viable.

This is a realistic static-route troubleshooting pattern because it distinguishes between configured intent and operational state.

Exam trap

A frequent exam trap is to confuse the presence of a static route in the configuration with its presence in the routing table. Candidates often overlook the fact that a static route pointing to an administratively down interface will not be installed, leading to the mistaken belief that the route is missing due to mask length or protocol requirements. Another trap is assuming static routes cannot use exit interfaces or require time synchronization, which is false.

This question tests the candidate's understanding of the difference between configured routes and operationally valid routes, focusing on interface state as the critical factor for route installation.

Why the other options are wrong

Incorrect because static routes can reference exit interfaces directly; Cisco routers support static routes with either next-hop IP addresses or exit interfaces.

Incorrect because the subnet mask length (such as /16 vs /24) does not prevent a static route from being installed; the issue is the interface state, not the mask.

Incorrect because static routes do not depend on NTP or time synchronization for installation; this is unrelated to static routing behavior.

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284

MCQhard

A network engineer is troubleshooting OSPFv3 adjacency between two directly connected Cisco routers, R1 and R2, both running IOS-XE. The engineer configures OSPFv3 on both routers but notices that the adjacency does not form. The engineer runs 'show ospfv3 neighbor' on R1 and sees no neighbors. What is the most likely cause of this issue?

A.The OSPFv3 process ID must match on both routers.

B.The interface GigabitEthernet0/0 is missing the 'ospfv3 1 ipv6 area 0' command.

C.The link-local addresses are not in the same subnet.

D.The router ID 1.1.1.1 is duplicated on R2.

AnswerB

With OSPFv3, enabling the OSPF process globally is not enough; each participating interface must be explicitly activated with the 'ospfv3 1 ipv6 area 0' interface-level configuration. This command assigns the interface to the OSPFv3 process 1 for address family IPv6 and places it into area 0. Without this command, the router will not send or listen for OSPFv3 Hello messages on GigabitEthernet0/0, so no neighbor adjacency can ever form. That is exactly why R2's neighbor entry is missing from the 'show ospfv3 neighbor' output.

Why this answer

OSPFv3 requires explicit interface-level configuration to enable the protocol on a specific interface. The correct command is 'ospfv3 1 ipv6 area 0' (or 'ipv6 ospf 1 area 0' for the traditional OSPFv3 configuration). Without this command, the interface does not participate in OSPFv3, so no Hello packets are sent or received, preventing adjacency formation.

Exam trap

Cisco often tests the distinction between OSPFv2 (where enabling the protocol under the routing process automatically activates it on all interfaces with 'network' statements) and OSPFv3 (which requires explicit per-interface activation), leading candidates to overlook the mandatory interface-level command.

Why the other options are wrong

This is a common misconception; OSPFv3 uses the router ID for neighbor identification, not the process ID.

Link-local addresses are automatically configured and do not affect OSPFv3 adjacency as long as they are unique.

In this scenario, no neighbors are seen, indicating a more fundamental issue like OSPFv3 not being enabled on the interface.

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285

Multi-Selectmedium

A route table shows both a default route and a more specific route to 192.168.50.0/24. Which two statements describe how packets destined for 192.168.50.25 are handled?

Select 2 answers

A.The router prefers the 192.168.50.0/24 route because it is the longest prefix match

B.The default route is used only when no more-specific route matches

C.Administrative distance is compared before prefix length for forwarding decisions

D.The packet is load-balanced across both routes automatically

AnswersA, B

The 192.168.50.0/24 route wins because longest prefix match dictates that the most specific route among all matching entries is used. With a /24 mask, it matches a narrower address range than the /0 default route, making it the superior entry for any destination inside 192.168.50.0/24. Forwarding therefore uses that route's next hop directly.

Why this answer

Once routes are installed, packet forwarding follows longest prefix match. The /24 route is more specific than the default route, so traffic to 192.168.50.25 uses the /24 entry.

Exam trap

A frequent exam trap is assuming that administrative distance is compared before prefix length when selecting a route. Candidates might think that if the default route has a better administrative distance, it will be chosen over a more specific route. However, Cisco routers always apply the longest prefix match rule first, selecting the most specific route regardless of administrative distance.

Administrative distance only comes into play when multiple routes have the same prefix length. Misunderstanding this can lead to incorrect answers about how packets are forwarded, especially when both default and specific routes exist in the routing table.

Why the other options are wrong

Option C is incorrect because administrative distance is not compared before prefix length; prefix length is the primary factor in route selection, making this option a common misconception.

Option D is incorrect because Cisco routers do not load-balance between a default route and a more specific route; these routes are not considered equal-cost and the more specific route is always preferred.

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286

Multi-Selectmedium

Which TWO statements about interpreting routing table output are true? (Choose two.)

Select 2 answers

A.A route with a longer prefix length is always preferred over a route with a shorter prefix length, regardless of administrative distance.

B.A directly connected route has an administrative distance of 0 and is always preferred over any dynamic route for the same network.

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

D.The metric is used to compare routes from different routing protocols.

E.A static route configured with an administrative distance of 200 will be preferred over an OSPF route with AD 110 for the same network.

AnswersA, B

The longest-prefix match rule is the first criterion in the routing table lookup: a route with a longer subnet mask (e.g., /32) is always selected over a less specific route (e.g., /24) for the same destination, even if that less specific route has a much lower administrative distance. Administrative distance becomes relevant only after the router identifies the set of routes with the longest matching prefix length. For example, a static route to 10.0.0.0/24 with AD 1 will lose to an OSPF route to 10.0.0.0/32 with AD 110, because specificity determines the winning route before AD is ever considered.

Why this answer

Longest-prefix match always wins regardless of AD or route source (A correct), and directly connected routes have AD 0 (B correct). C is incorrect because among equal prefix lengths, lower AD wins. D is wrong because metric only compares same-protocol routes, while AD compares across protocols.

E fails because a higher AD (200) is less preferred than OSPF's 110.

Exam trap

Cisco often tests the misconception that administrative distance is the primary tie-breaker, but the trap here is that the longest prefix match rule always takes precedence, even over a directly connected route with AD 0.

Why the other options are wrong

A lower AD indicates a more trustworthy source, so the route with the lower AD is preferred, not the higher one.

Metrics are only comparable within the same routing protocol (e.g., OSPF cost vs. EIGRP composite metric). For different protocols, AD is used to select the best route.

A lower AD is preferred; OSPF AD 110 is lower than 200, so the OSPF route would be chosen.

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