R1 and R2 are directly connected using the interfaces shown in the exhibit. R1 can ping R2’s
interface, and R2 can ping R1’s interface. The IS-IS adjacency will not come up. What is causing
the adjacency to fail?
The correct levels are not configured under protocols isis.
The link MTU is too small to support IS-IS.
Authentication is not properly configured for the adjacency.
Both routers are configured as the DR, causing a conflict.