5-36z To make the configuration take effect, all BGP neighbors need to execute the reset bgp allcommand.z After the above configuration, because the MED attribute value of the route 1.0.0.0 learnt by SwitchC is smaller than that of the route 1.0.0.0 learnt by Switch B, Switch D will choose the route 1.0.0.0coming from Switch C.z If you do not configure MED attribute of Switch A when you configure Switch A, but configure thelocal preference on Switch C as following:# Define ACL 2000 to permit the route 1.0.0.0/8.[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[SwitchC-acl-basic-2000] quit# Create a routing policy named localpref, and specify node 10 with the permit matching mode for therouting policy. Set the local preference value of the route matching ACL 2000 to 200[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# Create a routing policy named localpref, and specify node 20 with the permit matching mode for therouting policy. Set the local preference value of the route to 100.[SwitchC] route-policy localpref permit node 20[SwitchC-route-policy] apply local-preference 100[SwitchC-route-policy] quit# Apply the routing policy localpref to the routing information from the peer 193.1.1.1.[SwitchC] bgp 200[SwitchC-bgp] peer 193.1.1.1 route-policy localpref importIn this case, because the LOCAL_PREF value of the route 1.0.0.0 learnt by Switch C is 200, which isgreater than that of the route 1.0.0.0 learnt by Switch B (Switch B does not configure the LOCAL_PREFattribute, the default value is 100), Switch D still chooses the route 1.0.0.0 coming from Switch C first.Troubleshooting BGP ConfigurationBGP Peer Connection Establishment ErrorSymptomWhen you use the display bgp peer command to display the BGP peer information, the connectionwith the opposite peer cannot be established.AnalysisTo establish a BGP peering relationship:z Both ends need to use the 179 port to establish TCP sessions.z Both ends need to exchange Open messages correctly.Troubleshooting1) Use the display current-configuration command to check the AS number configuration of theneighbor.2) Use the display bgp peer command to check the IP address of the neighbor.3) If a loopback interface is used, check whether the peer connect-interface command is configured.
