300-440 Question 55
Select 3You are configuring OSPF between two routers in your network. Despite matching configurations, the OSPF neighbor relationship is not forming. Upon investigation, you suspect authentication issues. Which configuration steps must be taken to ensure successful neighbor establishment using MD5 authentication?
- A
Enable OSPF authentication on the interface by specifying the 'ip ospf authentication message-digest' command
- B
Configure the same MD5 key ID and key string on both routers
- C
Set the OSPF area to 'authentication' mode using the 'area
authentication message-digest' command - D
Ensure the OSPF Hello and Dead intervals are identical on both routers
- E
Use the 'ip ospf authentication null' command to disable authentication while troubleshooting
Show answer and explanation
Correct answers: A, B, C
Explanation
To successfully establish an OSPF neighbor relationship with MD5 authentication, you must configure OSPF to use message-digest authentication on the interface, ensure the MD5 key ID and key string match on both routers, and enable authentication at the area level. These steps ensure that OSPF packets are authenticated and secure, allowing the neighbor relationship to form. Other settings, like Hello/Dead intervals, are important for general OSPF operation but do not directly resolve authentication issues.
- A. Correct.
Correct: Enabling MD5 authentication on the interface is necessary for OSPF to use message-digest authentication and validate neighbor relationships securely.
- B. Correct.
Correct: Both routers must have matching MD5 key IDs and key strings. If these do not match, the authentication process will fail.
- C. Correct.
Correct: Configuring the OSPF area with MD5 authentication ensures that authentication is enforced for OSPF packets within that area.
- D. Incorrect.
Incorrect: While matching Hello and Dead intervals is critical for OSPF neighbor formation, it does not directly address authentication issues.
- E. Incorrect.
Incorrect: Disabling authentication with 'ip ospf authentication null' contradicts the requirement to use MD5 authentication and will prevent secure neighbor establishment.