This document provides troubleshooting information for common problems with Open Shortest Path First (OSPF). To see more infomation, or to go to the next flowchart, click the command boxes in red.
There are no specific requirements for this document.
This document is not restricted to specific software and hardware versions.
The information in this document was created from the devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. If your network is live, make sure that you understand the potential impact of any command.
You can use an Embedded Event Manager (EEM) script to troubleshoot the links flapping.
For more information, refer to this Cisco Support Community document that describes how to use an EEM script in order to collect information from a router when there is an OSPF flap: Troubleshooting OSPF Flaps with EEM Script .
Note that the debug output from the debug ip ospf hello command shows the mismatch in hello parameters. Here is the sample debug output:
*Oct 12 14:03:32.595: OSPF: Send hello to 18.104.22.168 area 0 on FastEthernet1/0 from 192.168.12.2
*Oct 12 14:03:33.227: OSPF: Rcv hello from 22.214.171.124 area 0 from FastEthernet1/0 192.168.12.1
*Oct 12 14:03:33.227: OSPF: Mismatched hello parameters from 192.168.12.1
!--- Indicates that there is mismtached hello parameters from 192.168.12.1
*Oct 12 14:03:33.231: OSPF: Dead R 2 C 3, Hello R 1 C 1 Mask R 255.255.255.0 C 255.255.255.0
*Oct 12 14:03:33.531: OSPF: Send hello to 126.96.36.199 area 0 on FastEthernet1/0 from 192.168.12.2