Which two statements are true about IS-IS adjacency formation? (Choose two.)

The correct answer is A. Level 1 only routers never form an adjacency with Level 2 only routers. C. For Level 1 adjacencies, area IDs must be the same. An L1 router does not form an adjacency with an L2 router, regardless of area. L1 routers form L1 adjacencies with L1 and L1-L2 routers in their area. L2 routers form L2 adjacencies with L2 and L1-L2 routers in their area or another area.

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Question

Options

ALevel 1 only routers never form an adjacency with Level 2 only routers.
BLevel 1 only routers always form an adjacency with Level 2 only routers.
CFor Level 1 adjacencies, area IDs must be the same.
DFor Level 2 adjacencies, area IDs must be the same.

How the community answered

(37 responses)

A
76% (28)
B
16% (6)
D
8% (3)

Explanation

An L1 router does not form an adjacency with an L2 router, regardless of area. L1 routers form L1 adjacencies with L1 and L1-L2 routers in their area. L2 routers form L2 adjacencies with L2 and L1-L2 routers in their area or another area.

Topics

#IS-IS adjacency#Level 1#Level 2#area ID

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