CCNA IP Routing Questions

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.

Candidates often recall that duplicate router IDs break adjacencies and assume any flapping must be caused by this. They miss the regular timing correlation with the dead interval.

Network type mismatch is a common OSPF troubleshooting topic, and candidates may attribute any flapping to mismatched types, overlooking the precise timer-derived timing.

Authentication problems are a frequent first guess for adjacency failures. The flapping behavior here contradicts a permanent rejection.

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.

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

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

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

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

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

Thinking that recursive static routes are prone to loop suppression, rather than understanding that the route is simply withdrawn when the next-hop is no longer reachable.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

This option is incorrect because OSPF neighbor relationships do not depend on matching hostnames. Hostnames are administrative identifiers and do not affect OSPF protocol operations or LSA exchanges.

This option is incorrect because a /30 subnet is a standard subnet size for point-to-point links and does not prevent OSPF from operating or forming adjacencies. OSPF works normally over /30 subnets.

This option is incorrect because OSPF runs over routed interfaces and does not require interfaces to be configured as switch trunks. Trunking is related to VLAN tagging and switching, not OSPF adjacency.

The next-hop should be R3 (10.0.0.6), not R2 (10.0.0.2).

The AD must be higher than OSPF's 110 (e.g., 150) to act as a floating static route.

The destination network should be 203.0.113.0/24, not a default route.

Administrative distance of 1 matches the default AD of a static route, so the floating route would not be less preferred; it needs a higher AD (e.g., 200) to act as a backup.

Using R1's own interface IPv6 address as next-hop would create a route pointing to itself, not to R2, and would not reach the loopback network.

The default route should use the default administrative distance (1) to remain the primary route; setting it to 200 would make it equal to the floating static route, causing unpredictable behavior.

Authentication mismatches prevent OSPF neighbors from reaching the 2-Way state by blocking bidirectional communication. Since the neighbors here have reached 2-Way, authentication mismatch is unlikely the cause.

Configuring the network type as point-to-point is not required on Ethernet segments and would change the adjacency formation behavior rather than explain the current normal 2-Way state with DROTHER routers.

Duplicate router IDs cause adjacency failures and routing problems but do not cause neighbors to remain in the 2-Way state with DROTHER routers. The output does not indicate a router ID conflict.

The static default route has an administrative distance of 200, which is higher than OSPF's default distance of 110. Therefore, OSPF's route is preferred, and the static route does not override it. Manual configuration does not bypass administrative distance; the router always prefers the lower distance.

Load balancing requires multiple routes with equal administrative distance and metric. Here, OSPF and the static route have different administrative distances (110 vs. 200), so they are not equal. The router will only use the best route (OSPF) and not load-balance.

Overlapping default routes are common and do not cause the router to ignore them. The router uses the route with the lowest administrative distance (OSPF) and ignores the static route unless OSPF fails. There is no conflict that would cause both to be ignored.

This option is incorrect because it assumes the router compares OSPF and EIGRP metrics directly. Metrics from different protocols are not comparable until administrative distance is considered, so the lower OSPF metric does not guarantee route installation.

This option is incorrect because load balancing occurs only when multiple equal-cost routes exist within the same routing protocol. Routes from different protocols are not automatically load-balanced simply because they reach the same destination.

This option is incorrect because the router automatically selects the best route using its decision process based on administrative distance and metric. Manual intervention is not required for route installation in this scenario.

The OSPF /16 route is less specific than the static /24 route. Although OSPF is a dynamic routing protocol, the router prefers the route with the longer prefix length, so this option is incorrect.

The default route is only used when no specific matching route exists. Since both OSPF and static routes cover the destination, the default route is not used here, so this option is incorrect.

Overlapping prefixes are normal in routing tables and do not prevent route selection. The router resolves overlaps using longest-prefix match, so this option is incorrect.

The track command is missing the decrement value; without it, the router will not adjust its priority when the interface fails.

The preempt command is missing; without preempt, a router with higher priority cannot take over the active role.

The track command uses a decrement of 10 instead of the required 20, so the priority drop is incorrect.

The router-ID is derived from the highest IP address on a loopback or physical interface, never from a MAC address.

A router-id change does not take effect immediately; you must clear the OSPF process or reload the router.

Router-IDs must be unique per router, not identical across all routers in the area.

The router does not discard the OSPF route; it installs both /16 and /24 entries because they represent different network-specific entries.

The traffic matches the /24 route, not the /16, so it would be forwarded via the EIGRP next-hop.

The /24 is a subset; traffic outside 172.16.10.0/24 matches only the /16 OSPF route.

0.0.0.0/0 is the IPv4 default route; the correct IPv6 default prefix is ::/0.

A floating static route must have a higher AD, not lower, so that it is less preferred and only installed when the primary (lower AD) route is lost.

Cisco IOS requires the next-hop to be reachable, but it does not have to be directly connected. As long as a route exists to reach that next-hop (even recursively), the static route can be installed.

It skips the more targeted hypothesis that an access control list is selectively blocking R1. The candidate mistakenly assumes that a unidirectional reachability problem is always caused by a missing return route.

This option investigates a Layer 3 adjacency that the successful R2-to-R3 ping has already validated. Candidates often default to checking neighbor state without considering the evidence that rules it out.

Candidates may recall MTU as a cause of intermittent connectivity issues, but here the symptom is a total failure from one source, making MTU a low-probability next step.

This option is incorrect because static routes do not inherently block traffic; they simply define paths for routing packets. A static route allows traffic to specific destinations, rather than blocking unknown ones.

This option is wrong because the static route configured does not limit routing to a single host; instead, it typically defines a broader range or a default route for multiple destinations.

This option is wrong because static routes do not inherently advertise routes into OSPF; they simply define a path to a specific destination. The question specifically asks about the function of a static route, which does not involve OSPF route advertisement.

This option is incorrect because OSPF process IDs are locally significant and do not need to match between routers. Different process IDs do not prevent adjacency formation.

This option is incorrect because the interfaces are in the same IPv4 subnet (10.1.50.0/24), which is a prerequisite for OSPF adjacency on broadcast networks.

This option is incorrect because OSPF commonly runs on Ethernet interfaces. Ethernet is a supported media type for OSPF neighbor discovery and adjacency formation.

Incorrect. The default route is less specific and only used when no matching connected or static route exists. Since a connected route matches, the default route is ignored.

Incorrect. The router does not load-balance equally between a connected route and a default route. It selects the single best route based on prefix length and administrative distance.

Incorrect. The router clearly has a matching connected route for the destination subnet, so it will use that route rather than discarding the traffic.

When the next-hop IP is not directly connected, the router does recursively resolve the address to determine the outgoing interface.

The 'network' command is for OSPFv2 and does not exist in OSPFv3; interface configuration is done via interface commands.

Setting the network type to point-to-point changes the OSPF link type; without matching configuration on R2, adjacency will fail.

Mismatched hello intervals prevent OSPF neighbor relationships from forming.

The static default route has an administrative distance of 200, which is higher than OSPF’s 110. Therefore, it is less preferred and will not be installed while the OSPF route is present, making this option incorrect.

Cisco routers do not perform per-packet load balancing between routes with different administrative distances. The route with the lowest AD is installed exclusively, so this option is incorrect.

Floating static routes do not suppress dynamic routes; instead, they serve as backups when dynamic routes are unavailable. Therefore, neither route is not installed is incorrect because the OSPF route will be installed.

The OSPF cost to the destination is not represented by the first number in brackets; it is the second number. Therefore, 110 cannot be the OSPF cost.

The number of hops is not indicated by the value 110. OSPF does not use hop count as its metric, so this option is incorrect.

The route age is shown separately after the next-hop IP address and interface, not inside the brackets. Thus, 110 does not represent route age.

Common misconception that metrics are compared across different routing protocols. In reality, AD is evaluated first, and only routes from the same protocol with equal AD are compared by metric.

Mistaking ECMP as the mechanism for selecting between two routes from different sources; in this scenario, the static route's AD disqualifies the OSPF route entirely.

Misunderstanding that IP addresses, not administrative distance or metrics, influence path selection.

The 'summary-address' command is not valid for OSPF; it is used in EIGRP and BGP.

The 'ip summary-address ospf' command is used for external route summarization, not for summarizing internal OSPF routes within an area.

The mask 255.255.255.0 is too specific and only covers a single /24 network, not the required range.

The specific factual error: EIGRP does not use 'network 0.0.0.0' to advertise a default route; default routes are typically redistributed or generated via 'ip default-network' or redistribution. Removing the EIGRP default route would break the intended primary path.

The specific factual error: Administrative distance is the primary factor for route selection between different routing protocols or sources. Changing the EIGRP metric does not affect the comparison with a static route.

The specific factual error: The 'ip route' command syntax is 'ip route prefix mask {next-hop | interface} [distance] [name] [permanent] [tag tag]'. There is no metric parameter. The correct way to make a static route less preferred is to set a higher administrative distance.

The specific factual error is that the instruction limits changes to R1 only; modifying R2 is not allowed.

The specific factual error is that the dead interval is not automatically derived from the hello interval; it must be set separately.

The specific factual error is that the hello interval is not automatically derived from the dead interval; both must be set explicitly.

Floating static routes require a higher AD, not lower, to be less preferred than the primary route.

Both IPv4 and IPv6 static routes can be configured as floating routes by setting a higher AD.

You can have multiple default static routes with different ADs, making the higher AD one a floating backup.

Incorrect timers (30/120) break adjacency, and 'passive-interface default' suppresses hellos on all interfaces, including the transit link.

Network type point-to-point on R1 does not match R2's default broadcast, causing a type mismatch that prevents OSPF adjacency.

Omits the required 'passive-interface GigabitEthernet0/1' command, leaving hellos sending on that interface.

This option is incorrect because static routes do not inherently get overridden by default routes; rather, the routing table prioritizes routes based on their specificity and administrative distance.

This option is incorrect because the subnet mask of the destination IP does not affect the functionality of static routes in this context; static routes can operate with various subnet masks without being limited to /16 or /24.

This option is incorrect because static routes can coexist with dynamic routing protocols like OSPF; they do not require OSPF to be disabled to function properly.

The network statement is syntactically correct and covers the interface IP address, so it does enable OSPF process on that interface (subject to the passive-interface setting).

The configuration shows 'no shutdown', indicating the interface is enabled. Administrative down would require the 'shutdown' command or lack of 'no shutdown'.

The output clearly shows 'area 0' in both routers' OSPF configurations, so area mismatch is not the cause.

Candidates may confuse adjacency failures with DBD exchange problems, but network type mismatch leads to a different state (2-WAY).

Candidates think duplicate Router IDs might cause DBD exchange failure, but duplicate IDs prevent neighbor discovery entirely.

Many associate EXSTART with any adjacency issue, but authentication errors prevent the neighbor from being listed at all.

The network address is wrong; the summary must start at 192.168.0.0, not 192.168.1.0.

The subnet mask /24 is too small; it does not summarize the three subnets.

The subnet mask /23 is too specific; it only covers two of the three subnets.

This option is incorrect because metric values are only compared among routes learned from the same routing protocol. The OSPF metric of 30 is irrelevant when compared to a static route, which is a different routing source with a lower administrative distance.

This option is incorrect because routers do not install multiple routes to the same prefix from different routing protocols unless they have equal administrative distance and are configured for load balancing. Here, the static route’s lower AD prevents the OSPF route from being installed.

This option is incorrect because the router does not delay route installation until a full SPF recalculation. Route selection is immediate based on administrative distance and metric rules. SPF recalculation only affects OSPF route selection, not cross-protocol comparisons.

Uses a /24 mask, which does not match the /32 loopback address, potentially leading to incorrect routing.

Uses next-hop 192.168.1.1, which is not directly reachable over the serial link to R2.

Creates a default route, which is not a host-specific static route as required.

Option B, 10.20.0.0/23, is incorrect because it only encompasses two of the four specified networks (10.20.0.0/24 and 10.20.1.0/24), failing to include the other two networks (10.20.2.0/24 and 10.20.3.0/24).

Option C is incorrect because it only summarizes a single network (10.20.0.0/24) and does not encompass the other three networks (10.20.1.0/24, 10.20.2.0/24, 10.20.3.0/24) that need to be included in the summary route.

Option D (10.20.0.0/21) is incorrect because it encompasses a larger range of addresses than required, including networks that are not part of the specified four networks, which are only within the /24 range of 10.20.0.0 to 10.20.3.0.

Preempt is not already enabled—otherwise both routers would not show as active. Failing to enable preempt leaves the split‑brain condition unresolved.

The virtual IP 192.168.1.254 is correctly assigned to the HSRP group; changing it would replace the default gateway for all hosts, breaking connectivity.

Removing tracking from R2 is irrelevant; the problem is R1's missing preempt and low priority, not R2's configuration. Both routers showing active is not caused by tracking on R2.