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AR BGP Peer Relationship Fails to Be Established

Latest reply: Sep 23, 2017 09:04:47 2401 1 0 0 0

Hi, everyone! Today I’m going to introduce why AR BGP Peer Relationship Fails to Be Established.

1.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:

l  BGP packets fail to be forwarded.

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

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

l  The peer AS number is incorrect.

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

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

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

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

l  The peer ignore command is configured on the peer.

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

2.Troubleshooting Flowchart

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

Figure 1-1 shows the troubleshooting flowchart.

Figure 1-1 Troubleshooting flowchart for the failure to establish the BGP peer relationship

20170923155229720001.png

 

3.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

                     Step 1    Run the ping command to check whether BGP peers can successfully ping each other.

l  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 -spacketsize 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.

l  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 19.2.6.1.1 The Ping Operation Fails.

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

                     Step 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

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

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

                     Step 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 223.5.0.109.

<Huawei> display bgp peer
 BGP local router ID : 223.5.0.109
 Local AS number : 41976
 Total number of peers : 12                Peers in established state : 4
 
  Peer            V          AS  MsgRcvd  MsgSent  OutQ  Up/Down       State PrefRcv
  8.9.0.8         4         100     1601     1443     0 23:21:56 Established   10000
  9.10.0.10       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.

l  If the peer router ID conflicts with the local router ID, run therouter 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.

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

                     Step 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 : 223.5.0.109
 Local AS number : 41976
 Total number of peers : 12                Peers in established state : 4
 
  Peer            V          AS  MsgRcvd  MsgSent  OutQ  Up/Down       State PrefRcv
  8.9.0.8         4         100     1601     1443     0 23:21:56 Established   10000
  9.10.0.10       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.

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

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

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

Run the display current-configuration configuration bgpcommand 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.

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

l       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.

 

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

l  Results of the preceding troubleshooting procedure

l  Configuration files, log files, and alarm files of the devices

----End

4.Relevant Alarms and Logs

Relevant Logs

BGP/3/STATE_CHG_UPDOWN

 

 

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gululu
Created Sep 23, 2017 09:04:47

thanks
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