OSPF not enabled on the interface or the corresponding interface is down.

Use network command to enable ospf on a particular network address.

Do “no shutdown” on the corresponding interface.

Use these commands:

OSPF Interface network address mismatch or subnet mask mismatch

Use these commands to find the output/find the mismatch:

Hello packet attribute mismatch I.e. interface hello interval or dead interval mismatch

Use these commands to find the output/mismatch:

OSPF interface configured as passive interface. Passive interfaces will not send hello packets.

Use these commands:

OSPF option field mismatch i.e. Ospf External Routing Capability mismatch due to stub area mismatch.

Configure same stubby-area.

Use these commands:

OSPF gets struck in two-way state when there is no DR/BDR elected i.e. both routers configured with priority 0

One router should be configured with a priority other than 0.

Use these commands:

OSPF can get stuck in Exstart/exchange state when the maximum transmission unit (MTU) do not match

Use these commands:

OSPF network type mismatch can cause timers (hello-interval) mismatch

Use these commands:

OSPF same router-id and loopback address

Use these commands:

 

OSPF area mismatch for virtual-link

Use these commands:

 

OSPF virtual-link router-id mismatch causing virtual-link down

Use these commands:

 

OSPF not enabled on the interface or the corresponding interface is down causing vlink down

Use these commands:

 

OSPF Multi-Area Adjacency happens only if the adjacency over the primary link is up.

Use these commands:

 

Multi-area configuration mismatch, such as area-id or process-id mismatch.

Use these commands:

 

Multi-Area link remains down, if the Router is not an "ABR"

Use these commands:

 

Multi-Area link will be removed if the primary link is down

Use these commands:

 

For multi access networks, it is required to specify the neighbor's interface address.

 

Multi-area configuration mismatch such as when the neighbor's address does not match any of the OSPF networks or the neighbor’s address is incorrect.

Use these commands:

 

Multi-area adjacency not applicable for the area on which virtual-link is enabled and vice-versa.

Use this command:

 

Daemon restarted after maximum router dead interval of all OSPF interfaces on restarting node

Use this command on restarting node:

 

Capability mismatch between restarting and helper node

Enable capability lls in router node.

Use these commands on both nodes:

 

Configurations not saved before restart

Use any one of these commands and check the saved file in /usr/local/etc:

 

Two routers on same segment get restarted at same time

Use these commands on restarting node:

 

Helper router got its LSDB changed while helping

Use these commands on restarting node:

 

“Resync timeout timer” is not sufficient to sync the whole database

Use these commands on restarting node: