JNCIS-ENT: Juniper Networks Certified Specialist – Enterprise Routing and Switching (2025) — Question 20

You are configuring an IS-IS IGP network and do not see the IS-IS adjacencies established.
In this scenario, what are two reasons for this problem? (Choose two.)

Answer options

• A. MTU is not at least 1492 bytes.
• B. IP subnets are not a /30 address.
• C. The Level 2 routers have mismatched areas.
• D. The Io0 interface is not included as an IS-IS interface.

Correct answer: A, D

Explanation

Option A is correct because IS-IS requires a minimum MTU of 1492 bytes for adjacencies to be established. Option D is also correct as the Io0 interface must be set up as an IS-IS interface for adjacencies to form. Options B and C are incorrect; while they may affect routing, they do not directly prevent IS-IS adjacencies from being established.