300-410 Question 2
Select 2A network engineer is configuring OSPF between two routers, R1 and R2, in the same area (Area 0). After completing the configuration, the OSPF neighbor relationship does not form. Upon reviewing the configuration and network setup, the engineer notices the following:
- The IP addresses of the interfaces on both routers are correctly assigned and can ping each other.
- Both routers are using the same OSPF area.
- The MTU sizes of the interfaces are mismatched between R1 and R2.
- Authentication is enabled on R1 but not on R2.
Which two issues must the engineer resolve to establish the OSPF neighbor relationship?
- A
Ensure the MTU sizes match on both router interfaces.
- B
Disable authentication on both routers.
- C
Configure OSPF authentication on R2 to match R1.
- D
Reassign the OSPF area to a different area on R1.
- E
Enable OSPF on additional interfaces on R2.
Show answer and explanation
Correct answers: A, C
Explanation
To establish an OSPF neighbor relationship, several parameters must match, including MTU sizes and authentication settings. In this scenario, the mismatched MTU sizes and inconsistent authentication configurations are the primary issues preventing the OSPF adjacency. Resolving these two issues will allow the routers to form the OSPF neighbor relationship properly.
- A. Correct.
OSPF requires the MTU sizes to match on both interfaces to form a neighbor relationship. Mismatched MTU sizes will prevent the adjacency from being established.
- B. Incorrect.
Disabling authentication on both routers is not necessary. Instead, authentication should be properly configured on both routers if it is enabled.
- C. Correct.
OSPF authentication must be configured consistently on both routers. In this case, R2 needs to be configured to match the authentication settings of R1.
- D. Incorrect.
Changing the OSPF area on one router would prevent the neighbor relationship because both routers need to be in the same area for OSPF adjacency.
- E. Incorrect.
Enabling OSPF on additional interfaces is not related to the problem described. The issue lies with the interfaces already configured for OSPF, not unconfigured ones.