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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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The BGP Peer Relationship Fails to Be Established

The BGP Peer Relationship Fails to Be Established

Common Causes

The BGP peer relationship fails to be established if the BGP peer relationship cannot enter the Established state.

This fault is commonly caused by one of the following:

  • BGP packets fail to be forwarded.

  • An ACL is configured to filter packets with the destination port TCP port 179.

  • The peer router ID conflicts with the local router ID.

  • The peer AS number is incorrect.

  • Loopback interfaces are used to establish the BGP peer relationship, but the peer connect-interface command is not configured.

  • Loopback interfaces are used to establish the EBGP peer relationship, but the peer ebgp-max-hop command is not configured.

  • The configurations of the peer valid-ttl-hops command are incorrect.

  • The number of routes sent by the peer exceeds the upper limit that is specified by the peer route-limit command.

  • The peer ignore command is configured on the peer.

  • The address families of devices on both ends are inconsistent.

Troubleshooting Flowchart

The BGP peer relationship fails to be established after the BGP protocol is configured.

Figure 19-5 shows the troubleshooting flowchart.

Figure 19-5  Troubleshooting flowchart for the failure to establish the BGP peer relationship

Troubleshooting Procedure

Context

NOTE:

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

Procedure

  1. Run the ping command to check whether BGP peers can successfully ping each other.
    • If BGP peers can successfully ping each other, there are available routes between BGP peers and link transmission is normal. In this case, go to Step 2.

      NOTE:

      Run the ping -a source-ip-address -s packetsize host command to detect the connectivity of devices on both ends. Because the source address is specified in this command, it is possible to check whether the two devices have available routes to each other. Check whether large Ping packets can be normally transmitted over the link by specifying the size of the Ping packet.

    • If the ping operation fails, check whether the two devices have routes to each other in routing table of each device.

      • If there are no routes to the peer, check the associated routing protocol configurations. For details, see the section The Ping Operation Fails.

      • If there are routes to the peer, contact technical support personnel.

  2. Check that no ACL is configured to filter the packets with the destination port TCP port 179.

    Run the display acl all command on the two devices to check whether an ACL is configured to filter the packets with the destination port TCP port 179.

    <Huawei> display acl all
     Total nonempty ACL number is 1
    
    Advanced ACL 3001, 2 rules
    Acl's step is 5
     rule 5 deny tcp source-port eq bgp
     rule 10 deny tcp destination-port eq bgp

    • If an ACL is configured to filter the packets with the destination port TCP port 179, run the undo rule rule-id destination-port command and the undo rule rule-id source-port command in the Advanced ACL view to delete the configuration.

    • If no ACL is configured to filter the packets with the destination port TCP port 179, go to Step 3.

  3. Check that the peer router ID does not conflict with the local router ID.

    View information about BGP peers to check whether the peer and local router IDs conflict. For example, if the IPv4 unicast peer relationship fails to be established, run the display bgp peer command to check whether the peer router ID conflicts with the local router ID. In the following example command output, the local router ID is 2.2.2.2.

    <Huawei> display bgp peer
     BGP local router ID : 2.2.2.2
     Local AS number : 41976
     Total number of peers : 12                Peers in established state : 4
    
      Peer            V          AS  MsgRcvd  MsgSent  OutQ  Up/Down       State PrefRcv
      10.9.0.8        4         100     1601     1443     0 23:21:56 Established   10000
      10.10.0.10      4         200     1565     1799     0 23:15:30 Established    9999
    NOTE:

    To check information about BGP peers in the BGP-VPNv4 address family or the BGP-VPN instance address family, run the display bgp vpnv4 all peer command.

    • If the peer router ID conflicts with the local router ID, run the router id command in the BGP view to change the two router IDs to different values. Generally, a loopback interface address is used as the local router ID.

    • If the peer router ID does not conflict with the local router ID, go to Step 4.

  4. Check that the peer AS number is configured correctly.

    Run the display bgp peer command on each device to check whether the displayed peer AS number is the same as the remote AS number.

    <Huawei> display bgp peer
     BGP local router ID : 2.2.2.2
     Local AS number : 41976
     Total number of peers : 12                Peers in established state : 4
    
      Peer            V          AS  MsgRcvd  MsgSent  OutQ  Up/Down       State PrefRcv
      10.9.0.8        4         100     1601     1443     0 23:21:56 Established   10000
      10.10.0.10      4         200     1565     1799     0 23:15:30 Established    9999
    NOTE:

    To check information about BGP peers in the BGP-VPNv4 address family or the BGP-VPN instance address family, you can run the display bgp vpnv4 all peer command.

    • If the peer AS number is incorrectly configured, change it to be the same as the remote AS number.

    • If the peer AS number is configured correctly, go to Step 5.

  5. Check whether BGP configurations affect the establishment of the BGP peer relationship.

    Run the display current-configuration configuration bgp command to check BGP configurations.

    Item

    Description

    peer connect-interface interface-type interface-number

    If two devices use loopback interfaces to establish the BGP peer relationship, run the peer connect-interface command to specify the associated loopback interface as the source interface that sends BGP packets.

    peer ebgp-max-hop hop-count

    When two directly connected devices use loopback interfaces to establish the EBGP peer relationship or two indirectly connected devices establish the EBGP peer relationship, run the peer ebgp-max-hop command and specify the maximum number of hops between the two devices.

    • When two directly connected devices use loopback interfaces to establish the EBGP peer relationship, the hop count can be any number greater than 1.

    • When two indirectly connected devices establish the EBGP peer relationship, specify the number of hops based on the actual situation.

    peer valid-ttl-hops hops

    If the peer valid-ttl-hops hops command is configured, check whether the value of hops is correct. The valid TTL range of the detected packet is [255 - hops + 1, 255]. hops specifies the number of hops between devices on both ends. The number of hops between two directly connected devices is 1.

    NOTE:

    The peer valid-ttl-hops command must be configured on devices on both ends.

    peer route-limit limit

    If the peer route-limit limit command is configured, check whether the number of routes sent by the peer exceeds the upper limit that is specified by limit. If the number of hops exceeds the upper limit, reduce the number of routes to be sent by the peer, and run the reset bgp ip-address command to reset the BGP peer relationship and trigger the re-establishment of the BGP peer relationship.

    peer ignore

    If the peer ignore command is configured on the peer, the peer is not required to establish the BGP peer relationship with the local device temporarily. To establish the BGP peer relationship between the peer and the local device, run the undo peer ignore command on the peer.

    Address family capability

    Check whether the address family capabilities of devices on both ends match. For example, in order to establish a BGP VPNv4 peer relationship, the peer enable command must be configured in the BGP-VPNv4 address families of both devices. If the peer enable command is configured on only one device, the BGP peer relationship on the other device is displayed as No neg.

  6. Please contact technical support personnel and provide them with the following information.

    • Results of the preceding troubleshooting procedure
    • Configuration files, log files, and alarm files of the devices

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Updated: 2019-05-10

Document ID: EDOC1000079719

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