Huawei Quidway S6500 Series Operation Manual page 265

Operation Manual - Routing Protocol
Quidway S6500 Series Ethernet Switches
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.
6.5 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.
Fault 2: BGP route cannot be advertised correctly after importing route of IGP with the
command network.
Troubleshooting: Route imported by command network should be same as a route in
current routing table, which should include destination segment and mask. Route
covering large network segment cannot be imported. For example, route 10.1.1.0/24
can be imported, while 10.0.0.0/8 may cause error.
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Chapter 6 BGP Configuration