JNCIS-SP: Juniper Networks Certified Specialist – Service Provider Routing (2021) — Question 31

You are setting up a new IS-IS adjacency between two devices. The new Level1 adjacency is not establishing.
What would cause this behavior?

Answer options

• A. The routers support a minimum MTU of 1492 bytes.
• B. The Level 1 routers have mismatched area IDs.
• C. The router ID has not been explicitly configured.
• D. The IP addresses are on different subnets.

Correct answer: B

Explanation

The correct answer is B because for Level 1 IS-IS adjacency to be established, the area IDs must match on both routers. Option A is irrelevant since MTU does not affect adjacency establishment, option C is incorrect because the router ID is not essential for this specific adjacency type, and option D is not a factor as long as the routers are in the same area.