Scenario
Refer to the topology. Your company 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.

R1 does not form an OSPF neighbor adjacency with R2. Which option would fix the issue?

A.
R1 ethernetO/1 is shutdown. Configure no shutdown command.

B.
R1 ethernetO/1 configured with a non-default OSPF hello interval of 25: configure no ip ospf
hello-interval 25

C.
R2 ethernetO/1 and R3 ethernetO/O are configured with a non-default OSPF hello interval of
25; configure no ip ospf hello-interval 25

D.
Enable OSPF for R1 ethernetO/1; configure ip ospf 1 area 0 command under ethernetO/1

Explanation:
Looking at the configuration of R1, we see that R1 is configured with a hello interval of 25 on
interface Ethernet 0/1 while R2 is left with the default of 10 (not configured).