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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 AR Router Fails to Establish an OSPF Adjacency with a Non-Huawei Device

An AR Router Fails to Establish an OSPF Adjacency with a Non-Huawei Device

Keywords

AR router, non-Huawei device, OSPF adjacency, failure, unable to reach the Full state, remain in the Exstart state

Abstract

An AR3260 connects to a non-Huawei device. However, the OSPF adjacency between the two devices cannot reach the Full state.

Problem Description

As shown in Figure 1-1, an AR3260 connects to a non-Huawei device. During the OSPF adjacency establishment, the state machine remains the Exstart state and cannot reach the Full state. As a result, routes cannot be learned correctly. During the query of information about packets obtained on the port that connects the AR3260 to the non-Huawei device, only Hello and database description (DD) packets are found.

Figure 19-24  An AR Router Fails to Establish an OSPF Adjacency with a Non-Huawei Device

Troubleshooting Procedure

  1. Check the AR3260 configuration.

    Run the display current-configuration command on the AR3260 to check the current parameter settings.

    # 
    interface GigabitEthernet0/0/1
     ip address 10.2.1.2 255.255.255.0
     ospf mtu-enable
    #

    The configuration file shows that the MTU detection function has been enabled on the interface that connects the AR3260 to the peer device. After this function is enabled, the interface will send DD packets that carry the MTU and check whether the MTU carried in the DD packets received from the peer interface exceeds the local MTU. If so, the OSPF adjacency remains the Exstart state and cannot reach the Full state.

  2. Run the undo ospf mtu-enable command on the AR3260 to set the MTU carried in the DD packets to be sent by the interface to 0. That is, disable the MTU detection function. Subsequently, the interface does not check the MTU when establishing an OSPF adjacency with the peer interface. After the configuration is complete, the two devices can establish an OSPF adjacency, and the problem is solved.

Root Cause

The MTU detection function has been enabled on the AR3260. When establishing an OSPF adjacency, the AR3260 checks whether the local interface uses the consistent MTU with the peer interface. If not, the OSPF adjacency remains the Exstart state.

Solution

During the OSPF adjacency establishment, disable the MTU detection function. By default, an AR device can establish an OSPF adjacency with the peer device when the MTU detection function is disabled.

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Updated: 2019-05-10

Document ID: EDOC1000079719

Views: 447781

Downloads: 4305

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