Router R2 is having adjacency problems with Router R1. Router R2 is stuck in ExStart state.
What is causing the problem?
A.
There is a physical and data link layer problem between R1 and R2.
B.
There is a misconfigured IP address on the R2 interface.
C.
The hello and dead intervals on R2 do not match R1.
D.
The interface MTU setting on R2 does not match R1.
Explanation:
Reference:
http://www.cisco.com/c/en/us/support/docs/ip/open-shortest-path-first-ospf/13684-12.html
Neighbors Stuck in Exstart/Exchange State:
The problem occurs most frequently when attempting to run OSPF between difference vendor’s routers. The problem occurs when the maximum transmission unit (MTU) settings for neighboring router interfaces don’t match. If the router with the higher MTU sends a packet larger that the MTU set on the neighboring router, the neighboring router ignores the packet.