CCNA Routing Questions

Uses 'ip route', which is for IPv4; IPv6 routes require 'ipv6 route'.

'ipv6 default-route' is not a valid Cisco IOS command.

'ip default-gateway' configures the management default gateway for IPv4, not an IPv6 routing entry.

The OSPF router ID is determined by the highest IP address on a loopback interface or the highest active physical interface IP at the time of OSPF process startup, not by passive-interface configuration. A passive interface does not influence router ID selection.

The passive-interface command only suppresses OSPF hello packets on that specific interface; OSPF continues to operate normally on other interfaces, forming adjacencies and exchanging routing information. It does not disable OSPF globally.

The passive-interface command is specific to OSPF and does not change the routing protocol. OSPF remains OSPF; it simply stops sending hellos on that interface. EIGRP has its own passive-interface command with similar behavior but does not convert protocols.

The specific factual error is that a floating static route must have a higher AD than the dynamic protocol to act as a backup; setting it equal or lower would disrupt the primary route.

The specific factual error is that removing OSPF is an extreme measure that breaks connectivity, whereas a floating static route is meant to be a seamless backup.

The specific factual error is that adding an extra static route is not the standard solution; Cisco recommends using the exit interface for directly connected next-hops to ensure route validity.

The specific factual error is that a reload is not required to apply MTU changes; the interface MTU is applied immediately, and the OSPF process can be cleared to re-establish adjacencies.

The specific factual error is that OSPF network type does not affect MTU requirements; MTU must match regardless of network type.

The specific factual error is that timer mismatches affect the INIT and 2-WAY states, while EXSTART is associated with MTU or database descriptor (DBD) packet issues.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Displays VLAN port membership; irrelevant to OSPF verification.

Shows STP topology; does not provide OSPF neighbor status.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

The output shows R2 is Active in its own group (20); priority only affects role election within the same group. The real problem is separate group numbers.

With mismatched authentication, the state would not be Active. The exhibit clearly shows Active on both routers, so authentication is not the cause.

Version mismatch would not change the displayed group number; the group number discrepancy is the direct evidence shown in the exhibit.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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