CCNP OSPF — Timed 10 Questions

Question 1

A network engineer is troubleshooting OSPF adjacency issues between two routers connected via a Gigabit Ethernet link. The engineer notices that the routers are stuck in the EXSTART state. Both routers have the same MTU of 1500 bytes. What is the most likely cause of this issue?

Accepted Answer

One router has a lower IP MTU configured on the interface, causing the DBD packet to be dropped.. When OSPF routers are stuck in the EXSTART state, it typically indicates a problem with the Database Description (DBD) packet exchange. Even though both routers have the same configured MTU of 1500 bytes, one router may have a lower IP MTU on its interface (e.g., due to a different interface MTU or encapsulation overhead), causing the DBD packet to be fragmented or dropped. Since OSPF DBD packets are not fragmented, a mismatch in the actual IP MTU prevents the adjacency from progressing beyond EXSTART.

Answer

The OSPF network type is point-to-point on one router and broadcast on the other.

Answer

The OSPF hello and dead intervals are mismatched.

Answer

The OSPF router IDs are the same.

Question 2

An enterprise network uses OSPF as its IGP. The network engineer notices that a particular route learned via OSPF is not being installed in the routing table, even though the neighbor adjacency is up and the route appears in the OSPF database. The route is an external route redistributed from EIGRP. What is the most likely cause?

Accepted Answer

The forwarding address in the type 5 LSA is not reachable via an OSPF internal route.. Option C is correct because OSPF requires the forwarding address (FA) in a Type 5 LSA to be reachable via an OSPF internal route (intra-area or inter-area) for the external route to be installed in the routing table. If the FA is not reachable, the router will ignore the LSA and not install the route, even though the LSA exists in the OSPF database and the neighbor adjacency is up.

Answer

The OSPF process ID is different on the routers.

Answer

The external route has a higher administrative distance than the internal route.

Answer

The OSPF metric for the external route is too high.

Question 3

A network engineer is configuring OSPF in a multi-area design. The engineer wants to reduce the amount of LSA flooding and the size of the LSDB in area 0. Which OSPF feature should be implemented on the ABR to achieve this goal?

Accepted Answer

Configure the ABR with an area filter-list to filter type 3 LSAs.. Option B is correct because configuring an area filter-list on the ABR allows the engineer to filter Type 3 summary LSAs entering or leaving area 0. This directly reduces LSA flooding and shrinks the LSDB in area 0 by preventing specific inter-area prefixes from being advertised into the backbone, without altering the area type or requiring additional redistribution.

Answer

Configure area 0 as a stub area.

Answer

Configure OSPF database overflow protection.

Answer

Configure the ABR as an ASBR.

Question 4

A network engineer is troubleshooting an OSPF adjacency issue between two routers connected via a serial link. The adjacency is stuck in the INIT state. The engineer has verified that the IP addresses are in the same subnet and that the link is up. What is the most likely cause?

Accepted Answer

The OSPF hello interval is mismatched between the two routers.. The INIT state in OSPF indicates that a router has received a Hello packet from its neighbor but the neighbor has not yet seen its own Router ID in the received Hello. A mismatched Hello interval causes the routers to send Hellos at different rates, so one router may not receive a Hello within the expected Dead interval, preventing the neighbor from seeing its Router ID in the received Hello and thus stalling the adjacency in INIT.

Answer

The OSPF router IDs are the same.

Answer

The OSPF process ID is different.

Answer

The OSPF network type is point-to-point on one router and point-to-multipoint on the other.

Question 5

A network engineer is designing an OSPF network with multiple areas. The engineer wants to ensure that routers in area 2 can reach networks in area 0, but they should not learn any external routes from other ASs. Which OSPF area type should be configured for area 2?

Accepted Answer

Stub area. A stub area blocks Type 5 LSAs (external routes from other ASs) while allowing Type 3 summary LSAs from area 0. This ensures routers in area 2 can reach networks in area 0 via inter-area routes but do not learn external routes, meeting the requirement exactly.

Answer

Not-so-stubby area (NSSA)

Answer

Totally stubby area

Answer

Standard area

Question 6

A network engineer is troubleshooting an OSPF issue where a router is not learning a route to a network that is advertised via a type 5 LSA from an ASBR. The engineer checks the OSPF database and sees the type 5 LSA, but the route is not in the routing table. The forwarding address in the LSA is 0.0.0.0. What is the most likely cause?

Accepted Answer

The ASBR is not reachable via an OSPF internal route.. When a Type 5 LSA has a forwarding address of 0.0.0.0, OSPF routers will use the ASBR as the next hop for the external route. For the route to be installed in the routing table, the ASBR must be reachable via an OSPF intra-area or inter-area route. If the ASBR is not reachable (e.g., no valid OSPF route to the ASBR's router ID), the Type 5 LSA is considered unreachable and is not installed, even though it exists in the OSPF database.

Answer

The type 5 LSA has a metric of 16777215.

Answer

The OSPF process ID on the ASBR is different from the other routers.

Answer

The type 5 LSA is being filtered by an outbound route filter.

Question 7

A network engineer is configuring OSPF on a router that connects to two different ISPs. The engineer wants to prefer one ISP for all external routes unless that ISP's link fails, in which case the other ISP should be used. Which OSPF feature should be used to influence the path selection for external routes?

Accepted Answer

Use the 'distance ospf external' command to set a higher administrative distance for external routes from the less preferred ISP.. Option B is correct because the 'distance ospf external' command allows you to set a higher administrative distance for external OSPF routes learned from a specific neighbor or source, making the routes from the less preferred ISP less trustworthy. When the preferred ISP's link fails, those routes are removed, and the router will then use the external routes from the backup ISP due to their lower administrative distance (or default distance if not changed). This directly influences path selection for external routes without altering OSPF metrics or interface costs.

Answer

Configure the OSPF cost on the interface connecting to the preferred ISP to a lower value.

Answer

Use the 'max-metric' command on the router connecting to the less preferred ISP.

Answer

Configure the OSPF network type to point-to-point on both interfaces.

Question 8

A network engineer is troubleshooting an OSPF adjacency issue between two routers connected via a Frame Relay network. The adjacency is stuck in the 2WAY state. The engineer has verified that the routers are in the same area and have matching hello/dead intervals. What is the most likely cause?

Accepted Answer

The OSPF network type is non-broadcast and the neighbors are not manually configured.. In OSPF over Frame Relay, the default network type for physical interfaces is non-broadcast (NBMA). On an NBMA network, OSPF does not send multicast Hello packets; instead, neighbors must be manually configured using the 'neighbor' command. Without manual neighbor configuration, the routers will not proceed past the 2WAY state because they cannot form a full adjacency without explicit neighbor discovery.

Answer

The OSPF router priority is set to 0 on both routers.

Answer

The OSPF area ID is different.

Answer

The Frame Relay map is missing for the broadcast keyword.

Question 9

A network engineer is configuring OSPF on a router that has multiple interfaces in the same area. The engineer wants to ensure that the router does not become the designated router (DR) on any of these interfaces. What should the engineer do?

Accepted Answer

Set the OSPF priority to 0 on all interfaces.. Setting the OSPF priority to 0 on all interfaces prevents the router from participating in the DR/BDR election process. A router with priority 0 will never become the DR or BDR on any segment, regardless of its Router ID or other factors. This is the only method that guarantees the router will not be elected as DR on any interface.

Answer

Configure the OSPF network type as point-to-point on all interfaces.

Answer

Use the 'ip ospf dr-priority' command to set a high priority on other routers.

Answer

Configure the router as an ABR.

Question 10

A network engineer runs the following command on Router R1:

R1# show ip ospf neighbor

Neighbor ID     Pri   State           Dead Time   Address         Interface
10.0.0.2          1   FULL/DR         00:00:32    192.168.1.2     GigabitEthernet0/0
10.0.0.3          1   2WAY/DROTHER    00:00:35    192.168.1.3     GigabitEthernet0/0

Based on this output, what can be concluded?

Accepted Answer

R1 is a DROTHER on this segment.. The output shows R1 has a neighbor with state 2WAY/DROTHER (10.0.0.3), which indicates that R1 is also a DROTHER on this broadcast multiaccess segment. The FULL/DR neighbor (10.0.0.2) is the Designated Router, and since R1 is not the BDR (no FULL/BDR state), it must be a DROTHER.

Answer

R1 is the Backup Designated Router (BDR) on this segment.

Answer

R1 has a full OSPF adjacency with the neighbor 10.0.0.3.

Answer

The OSPF network type is point-to-point.