Fault Diagnosis And Bgp Troubleshooting - Huawei Quidway S3500 Series Operation Manual

Operation Manual - Routing Protocol
Quidway S3500 Series Ethernet Switches
[Switch C-acl-basic-2000] rule deny source any
Define the route policy with the name of localpref, of those, the local preference
matching ACL 2000 is set as 200, and that of not matching is set as 100.
[Switch C] route-policy localpref permit node 10
[Switch C-route-policy] if-match acl 2000
[Switch C-route-policy] apply local-preference 200
[Switch C-route-policy] route-policy localpref permit node 20
[Switch C-route-policy] apply local-preference 100
[Switch C-route-policy] quit
Apply such route policy to the BGP neighbor 193.1.1.1 (Switch A)
[Switch C] bgp 200
[Switch C-bgp] peer 193.1.1.1 route-policy localpref import
By then, due to the fact that the Local preference attribute value (200)of the route
1.0.0.0 learned by Switch C is more than that of Switch B(Switch B is not configured
with local Preference attribute, 100 by default), Switch D will also first select the route
1.0.0.0 from Switch C.

5.5 Fault Diagnosis and BGP Troubleshooting

Fault 1: The neighborhood cannot be established (The Established state cannot be
entered).
Troubleshooting: The establishment of BGP neighborhood needs the router able to
establish TCP connection through port 179 and exchange Open packets correctly.
Perform the check according to the following steps:
Check whether the configuration of the neighbor's AS number is correct.
Check whether the neighbor's IP address is correct.
If using the Loopback interface, check whether the connect-source loopback
has been configured. By default, the router uses the optimal local interface to
establish the TCP connection, not using the loopback interface.
If it is the EBGP neighbor not directly connected, check whether the peer
ebgp-max-hop has been configured.
Use the ping command to check whether the TCP connection is normal. Since one
router may have several interfaces able to reach the peer, the extended ping -a
ip-address command should be used to specify the source IP address sending
ping packet.
If the Ping operation fails, use display ip routing-table command to check if there
is available route in the routing table to the neighbor.
If the Ping operation succeeds, check if there is an ACL denying TCP port 179.If the
ACL is configured, cancel the denying of port 179.
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Chapter 5 BGP Configuration