3com DUA1750-2BAA01 Manual De Usuario
3Com Switch 8800 Configuration Guide
Chapter 21 BGP Configuration
21-33
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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
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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.
21.5 Troubleshooting BGP
Symptom 1: The neighborhood cannot be established (The Established state cannot
be entered).
Solution: 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:
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Check whether the configuration of the neighbor's AS number is correct.
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Check whether the neighbor's IP address is correct.
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If using the Loopback interface, check whether the connect-source loopback
command has been configured. By default, the router uses the optimal local
interface to establish the TCP connection, not using the loopback interface.
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If it is the EBGP neighbor not directly connected, check whether the peer
ebgp-max-hop command has been configured.
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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.
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If the Ping operation fails, use the display ip routing-table command to check if
there is available route in the routing table to the neighbor.
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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.
Symptom 2: BGP route cannot be advertised correctly after route of IGP is imported
with the network command.
Solution: Route imported by the network command should be same as a route in the
current routing table, which should include destination segment and mask. Route