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AR Router Troubleshooting Guide

This Product Documentation provides guidance for maintaining AR Enterprise Router, covering common information collection and fault diagnostic commands, typical fault troubleshooting guide, and troubleshooting.
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An OSPF Routing Loop Occurs Because Router IDs of Devices Conflict

An OSPF Routing Loop Occurs Because Router IDs of Devices Conflict

Fault Symptom

In the networking shown in Figure 19-11, OSPF multi-instance is run between PEs and CEs. The CEs are Layer 3 switches of other manufacturers. The PEs deliver OSPF default routes to interwork the networks of two cities.

CE1 can successfully ping PE1, and CE2 can successfully ping PE2. When a CE pings a remote peer or a device on the remote network, packet loss occasionally occurs.

Figure 19-11  Network diagram of an OSPF routing loop that occurs because router IDs of the devices conflict

Fault Analysis

  1. 10.1.1.33 is the largest IP address in the VPN instance to which the two PEs are bound, and the following command is run to configure OSPF multi-instance:

    <PE1> ospf 4 vpn-instance www

    PE1 and PE2 select 10.1.1.33 as their router ID.

  2. On CE1, the router ID of PE1 is 10.1.1.33; on CE2, the router ID of PE2 is also 10.1.1.33.
  3. Debugging information on the CEs shows that a device with the router ID 10.1.1.33 sends LSAs every five seconds and the sequence numbers of LSAs are incremental and unstable.
  4. The CEs receive LSAs sent by two devices with the same router ID. This causes the OSPF default routes in the routing tables of the CEs constantly change. When the default route of CE1 is learned by CE2 and the default route of CE2 is learned by CE1, a routing loop occurs. As a result, routes are unreachable and packet loss occurs.

Procedure

  1. Run the ospf 4 router-id 10.2.2.9 vpn-instance www command on PE1 to specify the router ID of the OSPF multi-instance as the unique address of PE1, and run the ospf 4 router-id 10.2.2.10 vpn-instance www command on PE2 to specify the router ID of the OSPF multi-instance as the unique address of PE2.

    [PE1] ospf 4 router-id 10.2.2.9 vpn-instance www
    [PE2] ospf 4 router-id 10.2.2.10 vpn-instance www

  2. Restart the OSPF process associated with the VPN instance on PE1, and then perform the same operation on PE2. Services are restored after both OSPF processes restart.

Summary

Specify the router ID of OSPF multi-instance as the unique addresses of the PEs.

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Updated: 2019-05-10

Document ID: EDOC1000079719

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