JNCIP-SP: Juniper Networks Certified Professional – Service Provider (2022) — Question 53

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

Answer options

• A. Level 1 intermediate systems exchange routing information with Level 1 intermediate systems on other IS-IS areas.
• B. An IS-IS router sets the attached bit in the PDUs it sends to a Level 1 area to indicate that it is a backbone router.
• C. A Level 1 router can only form adjacencies with other Level 1 routers.
• D. Level 2 routers can form adjacencies with either Level 1 or Level 2 routers.

Correct answer: B, C

Explanation

Option B is correct because it describes how IS-IS routers indicate their backbone status to Level 1 areas by setting the attached bit. Option C is also correct as Level 1 routers can only form adjacencies with other Level 1 routers. Option A is incorrect since Level 1 intermediate systems do not exchange information across different IS-IS areas. Option D is incorrect because Level 2 routers can form adjacencies with Level 1 routers but not the other way around.