Scenario:
A customer network engineer has edited their OSPF network configuration and now your customer
is experiencing network issues. They have contacted you to resolve the issues and return the
network to full functionality.

The OSPF neighbour relationship has been lost between R1 and R3. What is causing this
problem?

A.
The serial interface in R1 should be taken out of the shutdown state.

B.
A neighbor statement needs to be configured in R1 and R3 pointing at each other.

C.
The R1 network type should be changed to point-to-multipoint non-broadcast.

D.
The hello, dead and wait timers on R1 need to be reconfigured to match the values on R3.

Explanation:
In order for two OSPF routers to become neighbors, they must have matching network types
across the links. In this case, we see that R1 has been configured as non-broadcast and R3 is
using point to point non-broadcast.

This can be seen by issuing the “show running-config” command on each router, or the “show ip
ospf interface” command: