CCNA IP Routing Questions

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that recursive static routes are prone to loop suppression, rather than understanding that the route is simply withdrawn when the next-hop is no longer reachable.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

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.

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 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.

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 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.

The mask must match the destination exactly; a /24 mask is too broad for a /32 host route.

The next-hop address must be directly connected; 192.168.1.1 is not a valid next hop from R1.

A default route is too broad; the requirement is for a specific route to the loopback address.

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.

This option is incorrect because the default route is less specific and only used when no other matching routes exist. Here, a more specific static route is present.

This option is incorrect because routers do not load balance equally between a specific static route and a default route; they prefer the most specific route.

This option is incorrect because the static route to 10.20.20.0/24 clearly matches the destination, making it a valid route for forwarding traffic.

The router-id is used only for OSPF router identification and does not need to be reachable; adjacency uses interface IP addresses.

OSPF does not require a specific subnet mask; it uses the configured mask on the interface as the network type.

OSPF is enabled on R2's G0/0; the issue is on R1's side where the passive-interface prevents hellos.

Option C is incorrect because summarization does not force routers to use only a default route; it aggregates routes but still allows routers to use more specific routes within the summary when available.

Option D is incorrect since route summarization is a routing optimization technique and is unrelated to PAT overload, which is a NAT function that translates multiple private IP addresses to a single public IP address with port differentiation.

Option E is incorrect because route summarization does not involve encryption of routing updates; encryption is a separate security feature not related to summarization.

Candidates may attribute arbitrary high metrics to a bandwidth calculation error, without noticing that only one LSA is affected.

A misunderstanding that filtering can somehow alter the metric rather than block the advertisement completely.

Confusion between external and inter-area route types leads candidates to think that metric-type manipulation could affect an internal summary LSA.

A floating static route with a higher AD is installed when the lower AD route is removed because of interface failure.

Floating static routes do not distinguish between physical and administrative interface down events; the primary route is removed in both cases.

The immediate cause is the missing exit interface; neighbor discovery configuration does not make an incomplete static route valid.

Candidates often assume OSPF is not working at all when a default route is missing, ignoring other OSPF routes in the table.

Candidates may assume any connectivity failure means an interface is disabled, but the routing table would show no connected network if the interface were shut down.

Candidates might think a misconfigured static route would cause the problem, but they overlook that the route would still appear in the table, just with a different next-hop.

The OSPF route (AD 110) has a lower metric but a higher administrative distance than EIGRP, so it loses.

The RIP route (AD 120) has the highest administrative distance and loses regardless of its hop count metric.

The static route with AD 95 loses to the EIGRP internal route (AD 90) because a lower AD is preferred.

This option is incorrect because the active route is determined by the administrative distance, not the metric. In this case, the EIGRP route has a lower administrative distance than the OSPF route, making it the active route.

This option is incorrect because only one route can be active for a given destination in a routing table, and having identical prefixes does not mean both routes can be active simultaneously. The router will select the route with the lower administrative distance, which is not addressed here.

This option is wrong because both routes are valid, and the router will select the route with the lower administrative distance, not the metric. The administrative distance of the EIGRP route is lower than that of the OSPF route, making it the active route.

This option is incorrect because Cisco routers do not install multiple default routes with different administrative distances simultaneously; only the route with the lowest AD is installed and used.

This option is incorrect because the backup route is not ignored permanently; it becomes active when the primary default route toward ISP-A fails, ensuring continuous connectivity.

The specific factual error is that OSPFv3 uses interface-level configuration, not network statements under the OSPF process.

The specific factual error is that setting a router ID alone does not activate OSPFv3 on an interface; OSPFv3 must be explicitly enabled on the interface.

The specific factual error is that 'passive-interface default' would actually prevent adjacency, not help form it.

Different hostnames do not affect OSPF adjacency since hostnames are used only for identification and management, not neighbor formation.

Different loopback addresses used for management do not influence OSPF adjacency on Ethernet interfaces, so they do not block neighbor relationships.

One router using SSH version 2 is unrelated to OSPF adjacency because SSH is a management protocol and does not impact routing protocol neighbor formation.

Candidates may think network type mismatch when they see no adjacency, but the exhibit does not indicate a mismatch and explicitly shows the passive state.

Timer mismatch is a classic troubleshooting trap, but the 'No Hellos (Passive interface)' message overrides any timer considerations.

Candidates may guess area mismatch as a cause, but the exhibit provides no evidence of it, while the passive-interface message is a direct cause.

A priority of 255 is the highest possible value, ensuring the router becomes the DR or BDR, not excluding it.

Priority 1 is the default and allows the router to be elected if it has the highest priority or Router ID.

Loopback interfaces are not used for DR/BDR elections; they are logical interfaces. The priority must be set on the physical interfaces connecting to other routers.

Administrative distance is only compared when two routes have the same prefix length. Here, the /32 route has a longer prefix, so it is chosen first.

Load balancing requires routes with identical prefix lengths and metrics. The /32 and /24 routes are treated as different destinations.

AD is only compared when routes have the exact same prefix length. The routing table can hold multiple overlapping routes as long as they differ in prefix length.

Incorrect because OSPF can handle multiple equal-cost routes and does not discard them; it uses all equal-cost paths to improve traffic distribution.

Incorrect since OSPF does not keep only the first learned route when multiple equal-cost paths exist; it installs all such routes for load balancing.

Incorrect because OSPF does not replace multiple valid equal-cost routes with a default route; default routes are used only when no specific routes exist.

Option A incorrectly states that the backup route is never considered because of its higher administrative distance. In reality, the higher AD is intentional to make it a floating static route that only activates when the primary route is removed.

Option C is incorrect because floating static routes do not require dynamic routing protocols to work. They are static routes with adjusted administrative distance and can function independently.

Option D is wrong because backup routes typically use a different next hop to provide true redundancy. Using the same next hop would not protect against next-hop failure.

Misunderstanding of route preference: a higher AD value does not keep a floating static installed when a better OSPF route becomes available.

Troubleshooting should follow the OSI model bottom‑up; immediately resetting processes skips basic interface‑level verification.

It targets a different root cause (OSPF adjacency failure due to MTU) that would manifest constantly, not only after interface recovery.

This option is wrong because a static route with a lower administrative distance than OSPF would take precedence over OSPF routes, making it active even when OSPF is available, contrary to the requirement of using the static route only when the OSPF route is unavailable.

This option is wrong because a second OSPF route with a lower metric would not serve as a backup to the existing OSPF route; instead, it would be preferred over the static route, which contradicts the requirement for the static route to be used only if the OSPF route disappears.

A default route with no next hop would not serve as a backup for an OSPF route because it lacks specificity and cannot direct traffic to a specific network. It would be ineffective in scenarios where a specific static route is needed when OSPF fails.

The question says R3 advertises the network via OSPF; a missing network command would contradict that, so the failure must be in adjacency formation.

The presence of other OSPF routes on the same interface disproves a blanket multicast ACL; the issue is specific to R3’s adjacency.

A duplicate router ID could prevent adjacency, but the scenario’s focus on passive-interface default provides a more common and direct cause for a total lack of adjacency when OSPF is correctly configured on the network.

Candidates may misinterpret a failed ping as indicating no default route exists, overlooking that the route is present but unusable.

Candidates may think a higher AD is blocking the route, but the AD is standard and not the issue.

A common troubleshooting step is to verify ip routing, but the exhibit clearly shows an active routing table.

Incorrect. OSPFv3 forms adjacencies using IPv6 link-local addresses, so global unicast addresses are not mandatory for adjacency formation or neighbor discovery.

Incorrect. Router IDs must be unique identifiers for OSPF routers. Identical router IDs cause adjacency failure, but they do not need to be identical to form adjacency.

Incorrect. IPv6 link-local addresses are automatically configured on interfaces and do not require DHCPv6. OSPFv3 uses these link-local addresses for neighbor communication.

OSPFv3 requires the link interface to be enabled to form neighbors; loopback-only configuration results in no neighbor relationship.

OSPFv3 must be enabled on the loopback interfaces to advertise their prefixes; otherwise, they remain unknown to the neighbor.

Both routers must have OSPFv3 enabled on the link interface to form an adjacency, and both loopbacks must be enabled to advertise their prefixes.

The specific factual error: The incorrect static route remains in the routing table, causing recursive routing failure. The router will still try to resolve the next-hop 10.0.0.1, which is its own interface, leading to a loop.

The specific factual error: The route does not have an administrative distance of 10, and using an exit interface instead of a next-hop IP is not the intended configuration. Also, the route would be installed with default AD 1, not 10.

The specific factual error is using an incorrect subnet mask and omitting the next-hop IP in the directly connected static route. The mask should match the point-to-point link (typically /30 or /31), and the next-hop must be specified to ensure the route is directly connected.

The specific factual error is using a /32 mask instead of the subnet mask of the link. A /32 route to the next-hop IP is a valid workaround but is not the standard practice; the question expects a directly connected route to the network containing the next-hop, not a host route.

The specific factual error is using the floating route's next-hop as the next-hop for the directly connected route. The directly connected route must be to the network containing 192.0.2.2, not to the backup next-hop.

This option is wrong because the OSPF route to 10.60.4.0/24 does not directly match the destination 10.60.4.17, which falls under the static route to 10.60.4.16/28. OSPF would not be preferred if a more specific static route exists.

The EIGRP route to 10.60.0.0/16 is not used for the destination 10.60.4.17 because it does not match the more specific subnet of 10.60.4.16/28, which is preferred in routing decisions.

This option is wrong because there is a valid static route to the destination 10.60.4.17 via the static route to 10.60.4.16/28, making it reachable. Therefore, stating 'no route at all' is incorrect in this context.

Setting the floating route AD to 1 makes it equal to the primary route's AD, defeating the purpose of a floating static route.

The primary route must have a lower AD than the floating route to be preferred. Setting it to 200 makes it equal to the backup, causing ambiguity.

The question states 'IPv4 and IPv6 static routes, default routes' and specifies an IPv6 next-hop. Ignoring IPv6 is a direct violation of the requirements.

You might think that OSPF routes are more reliable, but directly connected routes are always preferred regardless of AD.

You might confuse metric with prefix length; metric only matters when prefix lengths are equal.

A default route is only used when no more specific route exists; here a specific route exists.

This option is incorrect because both routers are configured to use the same OSPF area 0, so area mismatch is not the cause of adjacency failure.

Hostnames do not influence OSPF neighbor relationships; routers form adjacencies based on protocol parameters, not device names, so this option is invalid.

A /24 subnet mask does not block OSPF multicast traffic; OSPF uses multicast addresses that function normally on standard subnet masks, so this option is incorrect.