3Com Switch 7750 Configuration Guide Guide

360 CHAPTER 36: BGP CONFIGURATION
[SwitchD] bgp 200
[SwitchD-bgp] undo synchronization
[SwitchD-bgp] group in internal
[SwitchD-bgp] peer 195.1.1.2 group in
[SwitchD-bgp] peer 194.1.1.2 group in
■ To make the configuration take effect, all BGP neighbors need to execute the
reset bgp all command.
■ After the above configuration, because the MED attribute value of the route
1.0.0.0 learnt by Switch C is smaller than that of the route 1.0.0.0 learnt by
Switch B, Switch D will choose the route 1.0.0.0 coming from Switch C.
■ If you do not configure MED attribute of Switch A when you configure Switch
A, but configure the local preference on Switch C as following:
# Configure the local preference of Switch C
■ Create ACL 2000 to permit routing information sourced from network 1.0.0.0.
[SwitchC] acl number 2000
[SwitchC-acl-basic-2000] rule permit source 1.0.0.0 0.255.255.255
[SwitchC-acl-basic-2000] rule deny source any
■ Define a routing policy named localpref, and set the local preference of the
routes matching with ACL 2000 to 200, and that of those unmatched routes to
100.
[SwitchC] route-policy localpref permit node 10
[SwitchC-route-policy] if-match acl 2000
[SwitchC-route-policy] apply local-preference 200
[SwitchC-route-policy] quit
[SwitchC] route-policy localpref permit node 20
[SwitchC-route-policy] apply local-preference 100
[SwitchC-route-policy] quit
■ Apply this routing policy to the inbound traffic flows coming from BGP
neighbor 193.1.1.1 (Switch A).
[SwitchC] bgp 200
[SwitchC-bgp] peer 193.1.1.1 route-policy localpref import
In this case, because the local preference value of the route 1.0.0.0 learnt by
Switch C is 200, which is greater than that of the route 1.0.0.0 learnt by Switch B
(Switch B does not configure the local preference attribute, the default value is
100), Switch D still chooses the route 1.0.0.0 coming from Switch C first.
BGP Error
Configuration
Example
BGP Peer Connection
Establishment Error
Symptom 1: A BGP neighbor relationship cannot be established, that is the
connection with the opposite peer cannot be established.
Solution: The BGP neighbor establishment process requires using port 179 to
establish a TCP session and exchanging Open messages correctly. You can follow
these steps to solve the problem: