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.)
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 lo0 interface is not included as an IS-IS interface.
Option A suggests that the MTU is not at least 1492 bytes. This is correct because IS-IS requires a minimum MTU of 1492 bytes to establish adjacencies 1 . If the MTU is less than this, IS-IS adjacencies will not be established 1 .
Option D suggests that the lo0 interface is not included as an IS-IS interface. This is also correct because the loopback interface (lo0) is typically used as the router ID in IS-IS 1 . If the loopback interface is not included in IS-IS, it could prevent IS-IS adjacencies from being established 1 .
Therefore, options A and D are correct.
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