A network administrator is troubleshooting the OSPF configuration of routers R1 and R2. The
routers cannot establish an adjacency relationship on their common Ethernet link.
The graphic shows the output of the show ip ospf interface e0 command for routers R1 and R2.
Based on the information in the graphic, what is the cause of this problem?
A.
The OSPF area is not configured properly.
B.
The priority on R1 should be set higher.
C.
The cost on R1 should be set higher.
D.
The hello and dead timers are not configured properly.
E.
A backup designated router needs to be added to the network.
F.
The OSPF process ID numbers must match.
In order to form OSPF adjacencies, the following must match on the neighboring routers:
area ID
subnet
Hello and Dead timers
stub area flag
OSPF
By default, OSPF uses a 10-second hello timer and 40-second hold timer on broadcast and point-to-point links, and a 30-second hello timer and 120-second hold timer for all other network types. An interface’s hello timer can be adjusted:
Router(config-if)# ip ospf hello-interval
If we set Router1 to use a hello timer of 15 seconds and leave Router2 at its default setting of 10 seconds, they will not form an adjacency. Note that this behavior is different from EIGRP. If we enable OSPF hello packet debugging with debug ip ospf hello, the router reports mismatched hello parameters (specifically the hello and dead intervals):
http://packetlife.net/blog/2008/may/14/hello-timer-behaviors/