JNCIS-SP: Juniper Networks Certified Specialist – Service Provider Routing (2023) — Question 27

Which two statements are correct about IS-IS? (Choose two.)

Answer options

• A. For level 2 adjacencies, the area IDs must be the same.
• B. A level 1 only router can never form an adjacency with a level 2 only router.
• C. A level 1 only router can form an adjacency with a level 2 only router.
• D. For level 2 adjacencies, the area IDs can be different.

Correct answer: B, D

Explanation

Option B is correct because a level 1 only router operates within a single area and cannot communicate with a level 2 router that spans multiple areas. Option D is also correct as level 2 adjacencies can exist between routers with different area IDs, allowing for more flexible network topologies. Options A and C are incorrect as they contradict the fundamental principles of IS-IS routing behavior.