Troubleshooting OSPF

Introduction

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.

Prerequisites

Requirements

There are no specific requirements for this document.

Components Used

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.

Conventions

Refer to Cisco Technical Tips Conventions for more information on document conventions.

Main Flowchart

If you have the output of a show ip ospf neighbor, show ip ospf neighbor, or show tech-support command from your Cisco device, you can use the Cisco CLI Analyzer (registered customers only) to display potential issues and fixes. To use Cisco CLI Analyzer, you must have JavaScript enabled.

Troubleshoot OSPF Neighbor States

Refer to OSPF Neighbor States for neighbor state descriptions.

Troubleshoot the OSPF Routing Table

Troubleshoot OSPF Init State

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.

Troubleshoot OSPF MTU

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.

Troubleshoot OSPF Corrupt Packets

Troubleshoot OSPF Two-Way State

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.

Troubleshoot OSPF Links

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 .

Troubleshoot Full Adjacency

Troubleshoot External Link-State Advertisements

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.

Troubleshoot OSPF NBMA Networks

Refer to Problems with Running OSPF in NBMA Mode over Frame Relay for more information on common OSPF over NBMA network problems.

Troubleshoot Access Lists

Troubleshoot Neighbors over PRI

Troubleshoot Ping

Troubleshoot the OSPF Interface

Troubleshoot Frame Relay Environment

Troubleshoot External Route Problems

Troubleshoot Network Type

Troubleshoot OSPF Area Type

Troubleshoot the Hello/Dead Interval Mismatch

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 224.0.0.5 area 0 on FastEthernet1/0
 from 192.168.12.2
*Oct 12 14:03:33.227: OSPF: Rcv hello from 1.1.1.1 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 224.0.0.5 area 0 on
 FastEthernet1/0 from 192.168.12.2

Related Information

• OSPF Support Page
• Technical Support & Documentation - Cisco Systems