Scenario
Refer to the topology. Yourcompany has decided to connect the main office with three other
remote branch offices using point-to-point serial links.
You are required to troubleshoot and resolve OSPF neighbor adjacency issues between the
main office and the routers located in the remote branch offices.

An OSPF neighbor adjacency is not formed between R3 in the main office and R6 in the Branch3
office. What is causing the problem?

A.
There is an area ID mismatch.

B.
There is a PPP authentication issue; the username is not configured on R3 and R6.

C.
There is an OSPF hello and dead interval mismatch.

D.
The R3 router ID is configured on R6.

Explanation:
Using the show running-config command we see that R6 has been incorrectly configured with
the same router ID as R3 under the router OSPF process.