CCNA IP Routing Practice Test 25 — 15 Questions

Question 1

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

Accepted Answer

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

Answer

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

Answer

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

Answer

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

Question 2

A router learns a route to 172.16.0.0/16 via OSPF (administrative distance 110) and a route to 172.16.10.0/24 via EIGRP (administrative distance 90). No other overlapping routes exist. Which TWO statements about how the router handles these routes are correct?

Accepted Answer

Both the OSPF and EIGRP routes are installed in the routing table.. B is correct because the router installs both routes in the routing table when they have different prefix lengths. The EIGRP route to 172.16.10.0/24 (AD 90) is more specific than the OSPF route to 172.16.0.0/16 (AD 110). The router uses the longest prefix match rule for forwarding, so both routes coexist without conflict.

Answer

The router installs only the EIGRP route because it has a lower administrative distance.

Answer

Traffic to 172.16.10.100 is forwarded using the OSPF route.

Answer

The EIGRP route is used for all traffic destined to any address within 172.16.0.0/16.

Question 3

An enterprise network uses an IPv6 dual-stack design. Router R1 has a primary default route ::/0 via 2001:db8:1::1 with AD 1 and a floating default route with AD 10 via link-local address fe80::2. After the primary link fails, the floating route fails to install, and R1 loses all external connectivity. The administrator confirms the backup interface is up/up.

Accepted Answer

The floating static route uses a link-local next-hop but does not specify an exit interface, making the route incomplete.. A floating static route using a link-local next-hop (fe80::2) must also specify an exit interface (e.g., GigabitEthernet0/1) to be considered complete. Without the exit interface, the router cannot determine which interface to use for neighbor discovery, leaving the route incomplete and unable to be installed into the routing table. This is a common requirement for IPv6 static routes with link-local addresses, as the next-hop is not globally unique.

Answer

The administrative distance of the backup route is 10, so it is not installed while the primary route still exists.

Answer

The floating static route will be installed only if the primary link is administratively shut down, not after a physical failure.

Answer

The next-hop fe80::2 is unreachable because IPv6 neighbor discovery is disabled on the backup interface.

Question 4

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

Accepted Answer

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

Answer

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

Answer

The OSPF process IDs on R1 and R2 are mismatched.

Answer

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

Question 5

A network engineer notices that traffic from the router to server 192.168.10.5 is being sent over a slow backup link, even though the primary high-speed link is up. The routing table has an OSPF route for 192.168.10.0/24 via the primary link and a static host route to 192.168.10.5/32 via the backup link. Why is the backup link used for traffic to the server?

Accepted Answer

The static /32 route is a more specific match than the OSPF /24 route, so it is selected regardless of administrative distance.. The router uses the most specific matching route in the routing table to forward traffic. The static host route to 192.168.10.5/32 has a longer prefix length (32 bits) than the OSPF route for 192.168.10.0/24 (24 bits), making it a more specific match. Even though OSPF has a higher administrative distance, the longest prefix match rule takes precedence over administrative distance when both routes are present in the routing table.

Answer

The static route has an administrative distance of 1, which is lower than OSPF's 110, so it is always preferred.

Answer

The router is load-balancing between the two routes, and traffic is being hashed to the backup link for this particular flow.

Answer

The OSPF route is not installed in the routing table because the static route has a better AD.

Question 6

A network administrator has configured HSRP between RouterA and RouterB for VLAN 10. End hosts using the virtual IP 192.168.1.1 as their default gateway experience intermittent connectivity losses, and pings to 192.168.1.1 often fail. The output of 'show standby brief' on both routers shows the state as Active. What is the most likely cause?

Accepted Answer

The routers are configured with mismatched HSRP authentication methods.. When both routers show the HSRP state as Active, a 'dual-active' scenario exists, which causes intermittent connectivity because both routers forward traffic for the virtual IP. Mismatched HSRP authentication methods (e.g., one router using plain-text authentication and the other using MD5) prevent the routers from exchanging proper Hello messages, so they fail to negotiate a single Active router. This is the most likely cause because authentication mismatches break the HSRP adjacency, leading to both routers assuming the Active role.

Answer

The virtual IP address is configured on only one router.

Answer

The HSRP group number on one router is set to 0.

Answer

The priority on both routers is configured to the same value.

Question 7

Drag and drop the following steps into the correct order to configure Router R1 with OSPFv2 process 1 to form neighbor adjacencies only on GigabitEthernet0/1 while preventing OSPF hello packets on all other OSPF-enabled interfaces.

Accepted Answer

router ospf 1. First, enter OSPF router configuration mode. Then assign a Router ID (optional but good practice). Next, advertise the local subnet with a network statement to enable OSPF on interfaces. Then apply passive-interface default to suppress hellos on all OSPF interfaces. Finally, use no passive-interface to allow adjacency on the specific interface.

Question 8

Which TWO statements about floating static routes and default routes are correct?

Accepted Answer

A floating static route uses an administrative distance higher than that of the primary route to act as a backup.. A floating static route is configured with a higher administrative distance (AD) than the primary route. This ensures the floating route remains inactive in the routing table unless the primary route fails, at which point the router installs the floating static route as a backup. The higher AD makes it less preferred than the primary dynamic or static route.

Answer

A floating static route must have a lower administrative distance than the primary route to ensure faster convergence.

Answer

Floating static routes are supported only for IPv6, not for IPv4.

Answer

A default static route cannot be configured as a floating static route.

Question 9

Refer to the exhibit. A network engineer is troubleshooting an OSPF adjacency issue between R1 and R2. The output of the show ip ospf neighbor command on R1 shows the neighbor relationship with R2 stuck in the EXSTART/DROTHER state. What is the most likely cause?

Accepted Answer

MTU mismatch on the link between R1 and R2, causing DBD packets to be dropped.. The EXSTART/DROTHER state indicates that the routers have progressed beyond the 2-WAY state but are stuck during the Database Description (DBD) packet exchange phase. An MTU mismatch between R1 and R2 causes DBD packets to be dropped because the receiving router will reject packets larger than its configured interface MTU, preventing the routers from completing the master/slave election and database synchronization.

Answer

OSPF network type mismatch between R1 and R2, preventing full adjacency.

Answer

Duplicate OSPF Router IDs on R1 and R2, causing DBD packet rejection.

Answer

OSPF authentication mismatch on the link, causing DBD packets to be rejected.

Question 10

A technician is troubleshooting an OSPF adjacency problem: R1 and R2 are not forming a neighbor relationship. R1's OSPF configuration includes the command 'network 192.168.1.0 0.0.0.255 area 0'. R2's GigabitEthernet0/0 is configured with IP address 10.1.1.1/30 and is participating in OSPF area 0. The engineer verifies that physical connectivity is fine and OSPF is enabled on R2. What is the most likely cause?

Accepted Answer

R1's network statement does not include the subnet of the link connecting R1 and R2.. R1's network statement 'network 192.168.1.0 0.0.0.255 area 0' only enables OSPF on interfaces whose IP addresses fall within the 192.168.1.0/24 range. The link between R1 and R2 uses the 10.1.1.0/30 subnet (R2's GigabitEthernet0/0 is 10.1.1.1/30), so R1's interface on that link is not covered by the network statement. Without OSPF enabled on the connecting interface, R1 cannot send or receive OSPF hello packets, preventing neighbor adjacency formation.

Answer

The OSPF network type on R1's interface differs from the network type on R2's interface.

Answer

R1's router ID is not manually set and duplicates the router ID of R2.

Answer

Mismatched OSPF hello and dead intervals between the routers.

Question 11

Refer to the exhibit. A network technician is troubleshooting router R1, which cannot reach hosts on the internet. R1 is connected to an ISP router at 203.0.113.1. The exhibit shows the output of the show ip route command. What is the most likely cause of the issue?

Accepted Answer

A static default route is not configured on R1, and OSPF is not advertising a default route.. The exhibit shows that R1 has no default route (0.0.0.0/0) in its routing table, and the only routes present are OSPF-learned internal routes. Since R1 cannot reach the internet, the most likely cause is that no static default route is configured pointing to the ISP router (203.0.113.1) and OSPF is not injecting a default route into R1. Without a default route, R1 has no path for traffic destined outside its OSPF domain.

Answer

The OSPF neighbor relationship with the ISP router is down.

Answer

The interface connecting to the ISP router is in a shutdown state.

Answer

An incorrect next-hop address was specified in the static default route, making the route invalid.

Question 12

A network engineer notices that R1 is using the static route to 192.168.10.0/24 via next-hop 10.1.1.2 instead of the OSPF route via 10.2.2.2, even though the OSPF path has lower latency. What is the most likely cause?

Accepted Answer

The static route has a lower administrative distance than the OSPF route.. R1 prefers the static route over the OSPF route because static routes have a default administrative distance (AD) of 1, whereas OSPF has a default AD of 110. Since a lower AD indicates a more trustworthy route, the static route is installed in the routing table regardless of metric or latency. The OSPF route, despite having lower latency, is not used because AD is evaluated before metric.

Answer

The OSPF route has a higher metric than the static route.

Answer

Equal-cost multi-path (ECMP) is disabled for OSPF.

Answer

The static route is configured with a higher next-hop IP address, so it is preferred.

Question 13

Refer to the exhibit. A network administrator is troubleshooting an OSPF adjacency on R1's GigabitEthernet0/0 interface connected directly to R2. R2 is powered on and shows correct OSPF configuration, but the adjacency is stuck in the INIT or DOWN state. Based on the output, what is the most likely cause of the failure?

Accepted Answer

The OSPF passive-interface command has been applied to GigabitEthernet0/0, preventing hello packets from being sent.. The adjacency is stuck in INIT or DOWN state, which indicates that R1 is not receiving OSPF Hello packets from R2. The passive-interface command on GigabitEthernet0/0 prevents R1 from sending Hellos, so R2 never sees R1, and R1 may see R2's Hellos (stuck in INIT) or not (stuck in DOWN). This matches the symptom exactly, as passive-interface suppresses outgoing Hellos while still allowing the interface to be advertised.

Answer

The OSPF network type on R1's GigabitEthernet0/0 does not match the network type on R2.

Answer

The OSPF hello and dead timers on R1 do not match those configured on R2.

Answer

The GigabitEthernet0/0 interface on R1 has been assigned to a different OSPF area than R2's connected interface.

Question 14

A network engineer configures a static route: ip route 192.168.10.0 255.255.255.0 10.1.1.2. The next hop 10.1.1.2 is reachable via OSPF. Later, the engineer notices that the route to 192.168.10.0/24 has disappeared from the routing table. What is the most likely cause?

Accepted Answer

The OSPF route to 10.1.1.0/30 has been lost, making the next-hop address 10.1.1.2 unresolvable.. The static route to 192.168.10.0/24 uses 10.1.1.2 as the next-hop address. For a static route with a next-hop IP (rather than an exit interface) to be installed in the routing table, the next-hop must be reachable via a valid route in the routing table. If the OSPF route to the subnet containing 10.1.1.2 (e.g., 10.1.1.0/30) is lost, the next-hop becomes unreachable, and the static route is removed from the routing table. This is the most likely cause of the route disappearing.

Answer

The static route has a higher administrative distance than OSPF, so OSPF's route to 192.168.10.0/24 replaced it.

Answer

The static route uses a next-hop IP address that is not directly connected, which is unsupported on this platform.

Answer

A routing loop caused by recursive lookups has suppressed the static route to prevent loops.

Question 15

R1 loses its route to 192.168.20.0/24 whenever R2's GigabitEthernet0/0 interface flaps. The network engineer has configured a floating static route with an administrative distance of 200. The OSPF route has an AD of 110. After R2's G0/0 interface recovers, the floating static route appears in the routing table instead of the OSPF route. What should the technician do next?

Accepted Answer

Check the carrier delay timers on R2's GigabitEthernet0/0 interface.. When R2's GigabitEthernet0/0 interface flaps, the OSPF neighbor relationship goes down, causing R1 to lose the OSPF route. The floating static route (AD 200) then takes over. After the interface recovers, OSPF should re-establish and install its route (AD 110) over the static route. However, if the carrier delay timer on R2's interface is set too high, the interface may not come up quickly enough for OSPF to re-converge before the floating static route is already installed and preferred. Checking and adjusting the carrier delay timer ensures that the interface state change is propagated promptly, allowing OSPF to re-establish and replace the static route.

Answer

Adjust the administrative distance of the floating static route to 201.

Answer

Clear the IP routing table and reset the OSPF process on R1.

Answer

Verify that the MTU on R1 and R2's GigabitEthernet0/0 interfaces match.