CCNP Infrastructure Practice Question

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

• ✗

  The area authentication command must be configured on all routers in the area, but the interface command is optional.

  Why it's wrong here

  The area authentication command enables authentication for the area, but the interface command is required to specify the key. Without the interface command, no key is present, and authentication will fail. Both commands are necessary for MD5 authentication to work.

• ✗

  The key ID must match on both routers, but the key string can be different.

  Why it's wrong here

  OSPF MD5 authentication requires both the key ID and the key string to match on both routers. If the key string differs, authentication fails and the neighbor relationship will not form. This statement is false; both parameters must be identical.

• ✓

  The key ID and key string must match on both routers, and the area authentication command must be consistent.

  Why this is correct

  For OSPF MD5 authentication to succeed, both routers must have the same key ID, the same key string, and the same authentication type configured for the area or interface. The area authentication command enables MD5 for the area, and the interface command provides the key. If any of these parameters differ, the neighbor relationship will not form.

• ✗

  The router must be reloaded for the MD5 key to take effect.

  Why it's wrong here

  OSPF MD5 keys take effect immediately after configuration; no reload is required. The issue is not about applying the key but about matching parameters. A reload would not resolve a mismatch in key ID or key string.