— Exhibit —
Jun 12 02:56:06 R1 rpd[60735]: RPD_OSPF_NBRDOWN: OSPF neighbor 10.50.10.25 (realm ospf-v2 fe-0/0/4.0 area 0.0.0.0) state changed from Full to Init due to 1WayRcvd (event reason: neighbor is in one-way mode)
Jun 12 02:59:36 R1 rpd[60735]: RPD_OSPF_NBRUP: OSPF neighbor 10.50.10.25 (realm ospf v2 fe-0/0/4.0 area 0.0.0.0) state changed from Init to ExStart due to 2WayRcvd (event reason: neighbor detected this router)
Jun 12 02:59:36 R1 rpd[60735]: RPD_OSPF_NBRUP: OSPF neighbor 10.50.10.25 (realm ospfv2 fe-0/0/4.0 area 0.0.0.0) state changed from Exchange to Full due to ExchangeDone (event reason: DBD exchange of slave completed)
— Exhibit —

Refer to the Exhibit.
You notice that there is a problem with the OSPF adjacency between two routers, R1 and R2. The
relevant system logs from R1 are shown in the exhibit.
What would cause this behavior?

A.
R2 was dropping R1’s OSPF hello packets.

B.
R1 was dropping R2’s OSPF hello packets.

C.
R1’s interface went down and came back up.

D.
There is an OSPF hello timer mismatch between the two routers.

Explanation: