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.
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Refer to OSPF Neighbor States for neighbor state descriptions.
Refer to Why Does the show ip ospf neighbor Command Reveal Neighbors in the Init State? for an Init State problem description and troubleshooting steps.
Note: If the problem is related to Layer 2, check if a proxy ARP is enabled. If it is enabled, disable it, and use the clear ip arp command in order to clear the ARP cache.
Refer to Why Does the show ip ospf neighbor Command Reveal Neighbors Stuck in 2-Way State? for an OSPF Two-way State problem description and troubleshooting steps.
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
Refer to Common Routing Problem with OSPF Forwarding Address for a description of forwarding addresses in external LSA, and for troubleshoot steps concerning the most common problems with LSAs having non-zero forwarding addresses.
Refer to Problems with Running OSPF in NBMA Mode over Frame Relay for more information on common OSPF over NBMA network problems.
Note: Debug output from the debug ip ospf hello command shows the mismatch in hello parameters. Here is the sample debug output:
|debug ip ospf hello|
*Oct 12 14:03:32.595: OSPF: Send hello to 220.127.116.11 area 0 on FastEthernet1/0 from 192.168.12.2 *Oct 12 14:03:33.227: OSPF: Rcv hello from 18.104.22.168 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 22.214.171.124 area 0 on FastEthernet1/0 from 192.168.12.2
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Refer to Cisco Technical Tips Conventions for information on conventions used in this document.