200-301 Question 332
Single answerA network engineer has configured OSPFv2 on Router1 in a single area (Area 0). The engineer notices that Router1 is not forming an OSPF adjacency with its neighbor Router2. Upon investigating, the following configurations are found:
Router1: interface GigabitEthernet0/0 ip address 192.168.1.1 255.255.255.0 ip ospf 1 area 0 router ospf 1 router-id 1.1.1.1
Router2: interface GigabitEthernet0/0 ip address 192.168.1.2 255.255.255.0 ip ospf 1 area 0 router ospf 1 router-id 2.2.2.2
What could be the cause of the adjacency issue?
- A
The subnet mask on Router1 and Router2 does not match.
- B
The router IDs on Router1 and Router2 are not unique.
- C
The OSPF process IDs on Router1 and Router2 do not match.
- D
The OSPF area IDs on Router1 and Router2 do not match.
Show answer and explanation
Correct answer: B
Explanation
OSPF requires certain conditions to form an adjacency, including matching subnet masks, identical OSPF area IDs, and unique router IDs. In this scenario, the router IDs must be unique for adjacency to form. If there is a conflict in router IDs, OSPF will not establish an adjacency between the routers.
- A. Incorrect.
This is incorrect because both Router1 and Router2 have the same subnet mask (255.255.255.0) on their GigabitEthernet0/0 interfaces, which is necessary for forming an adjacency.
- B. Correct.
This is correct because OSPF requires all router IDs to be unique within the network. If the router IDs were not unique, OSPF adjacencies would not form.
- C. Incorrect.
This is incorrect because the OSPF process ID is a locally significant value and does not need to match between OSPF routers.
- D. Incorrect.
This is incorrect because both Router1 and Router2 are in the same OSPF area (Area 0), which is required for adjacency formation.