350-401 Question 432
Single answerA network administrator is configuring OSPFv2 between two routers, R1 and R2. The routers are directly connected and must establish a neighbor relationship. The administrator has configured the same area ID, network type, and MTU on both routers. However, the adjacency is stuck in the 'INIT' state. Upon further investigation, it is discovered that OSPF authentication has been configured. What is the MOST likely reason for the issue?
- A
Mismatched OSPF authentication types on R1 and R2
- B
Different OSPF router IDs configured on R1 and R2
- C
Incorrect OSPF area type configured on R1 and R2
- D
Multicast traffic for OSPF Hello packets is being blocked
Show answer and explanation
Correct answer: A
Explanation
For OSPF neighbor relationships to form, authentication configurations must match on both routers if authentication is enabled. This includes both the authentication type (plain-text or MD5) and the authentication key. In this scenario, the adjacency is stuck in 'INIT', which strongly indicates that there is an issue with the authentication configuration. Other factors, such as different router IDs or area types, do not impact the adjacency state in this manner.
- A. Correct.
Mismatched OSPF authentication types can prevent neighbor adjacencies from forming. If one router is using plain-text authentication and the other is using MD5, the neighbor relationship will not be established.
- B. Incorrect.
Different OSPF router IDs do not prevent adjacency formation. OSPF requires unique router IDs but mismatched IDs do not stop the process of forming a neighbor relationship.
- C. Incorrect.
Incorrect OSPF area types, such as stub or NSSA, can cause routing issues but do not prevent the formation of OSPF adjacencies if both routers share the same area.
- D. Incorrect.
Blocking multicast traffic for OSPF Hello packets (to 224.0.0.5) can prevent adjacency formation, but in this scenario, the adjacency is stuck in 'INIT', which indicates that Hello packets are being received but the response is not being processed correctly.