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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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Huawei uses machine translation combined with human proofreading to translate this document to different languages in order to help you better understand the content of this document. Note: Even the most advanced machine translation cannot match the quality of professional translators. Huawei shall not bear any responsibility for translation accuracy and it is recommended that you refer to the English document (a link for which has been provided).
ARP Troubleshooting

ARP Troubleshooting

Common Causes

The following table lists common ARP faults and provides possible causes.

Symptom

Possible Cause

ARP learning fails on an Ethernet sub-interface.

ARP broadcast is not enabled on the Ethernet sub-interface.

Too many ARP entries are learned.

ARP packets with the same source IP address continuously trigger ARP Miss messages within a period. An ARP attack may be initiated from this source IP address.

The remote device receives ARP requests but discards them.

The remote device receives a large number of ARP packets. The rate of ARP packets exceeds the CAR, so the device discards the ARP requests.

Ping operations between the local and remote devices fail at the beginning but succeed some time later.

STP is enabled on the two devices.

Troubleshooting Procedure

NOTE:

Saving the results of each troubleshooting step is recommended. If your troubleshooting fails to correct the fault, you will have a record of your actions to provide Huawei technical support personnel.

Procedure

  1. Check whether ARP broadcast is enabled on the sub-interface.

    Run the display this command in the sub-interface view to check the configuration of the sub-interface.

    If arp broadcast enable is not displayed, ARP broadcast is not enabled. Run the arp broadcast enable command to enable ARP broadcast on the sub-interface.

  2. Check the number of ARP entries on the device.

    Run the display arp statistics all command in the user view to check statistics about ARP entries.

    If the total number of static and dynamic ARP entries exceeds 500, check the number of users on the network:

    • If there are only a few users on the network, the large number of ARP entries may be caused by an ARP attack.
    • If there are many users on the network, more than 500 ARP entries are common to this network. In this case, use the following commands to improve the ARP learning speed:
      • Run the arp-miss speed-limit source-ip [ ip-address ] maximum maximum command to set a rate limit for ARP Miss suppression based on source IP address.
      • Run the cpu-defend-policy policy-name command to create an attack defense policy and enter the attack defense policy view. Then run the packet-type arp-miss rate-limit rate-value command to set a rate limit for ARP Miss messages sent to the CPU.

  3. Check whether multiple IP addresses map the same MAC address in the ARP table.

    • Run the display arp all command to check all ARP entries on the device.

    • If multiple IP addresses map the same MAC address in the ARP table, the device experiences an ARP attack. Run the arp learning strict command to enable strict ARP learning.

  4. Check whether STP is disabled.

    Run the display stp command in the system view to check the STP status.

    If the Protocol Status field displays enabled, run the stp disable command to disable STP.

  5. If the fault persists, collect the following information and contact technical support personnel.

    • Results of the preceding troubleshooting procedure
    • Configuration file, logs, and alarms of the device

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Updated: 2019-05-10

Document ID: EDOC1000079719

Views: 444011

Downloads: 4295

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