300-410 Question 82
Single answerA network administrator is troubleshooting an OSPFv2 issue where two routers, R1 and R2, are not forming a neighbor relationship. Both routers are in the same OSPF area and can ping each other. Upon reviewing the configuration, the administrator notices that R1 has the following configuration:
interface GigabitEthernet0/0 ip address 192.168.1.1 255.255.255.0 ip ospf 1 area 0
R2 has the following configuration:
interface GigabitEthernet0/0 ip address 192.168.1.2 255.255.255.0 ip ospf 2 area 0
What is the most likely cause of the OSPF neighbor relationship failure?
- A
The OSPF router IDs on R1 and R2 are not unique.
- B
The OSPF process IDs on R1 and R2 do not match.
- C
The OSPF hello and dead timers are mismatched between R1 and R2.
- D
The OSPF authentication settings on R1 and R2 are not configured.
Show answer and explanation
Correct answer: B
Explanation
In OSPF, the process ID is locally significant and does not impact neighbor relationships between routers. The provided configuration shows a mismatch in OSPF process IDs (1 on R1 and 2 on R2), but this does not prevent the formation of adjacency. Reviewing other possibilities, the configuration does not indicate issues with router IDs, hello/dead timers, or authentication settings, which are more critical for neighbor establishment. Therefore, the mismatch in process IDs is the most likely cause.
- A. Incorrect.
OSPF router IDs must be unique, but router IDs do not impact the formation of neighbor relationships as long as they are unique across the network.
- B. Correct.
OSPF process IDs are locally significant and do not need to match between routers to form a neighbor relationship. The issue is unrelated to the process ID mismatch.
- C. Incorrect.
If the hello and dead timers were mismatched, the routers would not form a neighbor relationship. However, there is no evidence in the configuration indicating a timer mismatch.
- D. Incorrect.
The problem is not related to authentication settings because the configuration does not show any authentication enabled on either router.