CCNA IP Routing Questions

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.

The IPv6 next-hop 2001:db8:0:1::2 is not reachable via a directly connected network; the router cannot resolve it.

The administrative distance must be set to a higher value (e.g., 200) to make it a floating route.

The IPv6 route fails due to recursive lookup failure; adding AD does not fix the next-hop issue.

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 route 172.16.0.0/16 matches the destination IP but is the least specific route with a /16 mask. Since more specific routes exist, the router will not select this route.

The route 172.16.20.0/24 also matches the destination but is less specific than the /25 static route. The router prefers the longer prefix match, so this route is not chosen.

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

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.

Creates a static route for a directly connected network that is already in the routing table, which is unnecessary.

On Ethernet interfaces, a static route must specify a next-hop IP address; specifying only an exit interface does not work for multi-access networks.

Creates a host route for the next-hop address itself, which is directly connected and already reachable, and does not provide a default route.

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.

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 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 in a network.

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.

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.

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.

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

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.

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.

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.

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.

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.

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.

Router-ID mismatch does not block OSPF adjacency; an OSPF router can still form a neighbor relationship even if the router-ID is not explicitly set (it will use the highest loopback IP) and can be changed without issue.

Network type mismatch would prevent adjacency, but the scenario does not indicate a mismatch; the default for Ethernet is broadcast, so both should be broadcast, and if one were changed to point-to-point they would not form, but that is not stated.

Passive-interface on the link interface (G0/0) would suppress hello packets and prevent adjacency, but the configuration correctly has passive-interface only on loopback0, so this is not the problem.

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.

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.

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.

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.

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.

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.

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.

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 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.

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.

The 'network' command is not valid for OSPFv3; OSPFv3 uses interface-level configuration.

This command is only valid in interface configuration mode.

The question explicitly says IPv6 unicast routing is already enabled, so this option includes an unnecessary step.

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.

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.

This describes a different mechanism (e.g., VRRP uses IP address as a tiebreaker only after priority).

The range is 0–255, not 0–100.

Preemption is not a default behavior.

Priority 0 is a special value, not the normal standby priority.

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.

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.

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.

The specific factual error is that changing network type is unnecessary and does not fix the passive-interface or timer mismatch problems.

The specific factual error is that the network command is already configured, so adding it again does not solve the adjacency problem.

The specific factual error is that loopback interfaces are intentionally excluded from OSPF, and forcing them to participate is not required and would be incorrect.

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.

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.

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.

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.

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.