587
passed SwitchD. Because SwitchC and SwitchB are not located in the same AS, the
SwitchA will not do metric comparison between the two switches. If the metric
comparison between different AS is needed, the command” bgp always-compare-med”
will be used. If this command is configured, the routes passed SwitchB are the best to
SwitchA. At this time, the following command may be added on SwitchA: “SwitchA
(config-router-bgp)# bgp always-compare-med”
14.8.5 BGP Troubleshooting Help
In the process of configuring and implementing BGP protocol, physical connection,
configuration false probably leads to BGP protocol doesn’t work. Therefore, the
customers should give their attention to points as follow:
First of all, to ensure correct physical connection;
Secondly, to ensure interface and link protocol are UP (execute show interface
instruction);
And startup BGP protocol (use router bgp command), configure affiliated IBGP and
EBGP neighbors (use neighbor remote-as command).
Notice BGP protocol itself can’t detect route, needs to import other routes to create
BGP route. Only it enables these routes to announce IBGP and EBGP neighbors by
importing routes. Direct-link routes, static route, and IGP route (RIP and OSPF) are
included in these imported routes. Network and redistribute (BGP) command are the
ways of imported routes.
For BGP, pay attention to the difference between the behaviors of IBGP and EBGP.
After configuration finishes, the command of show ip bgp summary can be used to
observe neighbor’s connections, so that all of the neighbors keep BGP connection
situation. And use show ip bgp command to observe BGP routing table.
If BGP routing problem still can’t be solved by debugging, please use debug
instructions like debug ip bgp packet/events etc, and copy DEBUG information in 3
minutes, then send them to ourTechnology Service Center.
14.8.5.1 Monitor And Debug Command
14.8.5.1.1 show ip bgp
Command: show ip bgp [<ADDRESS-FAMILY>] [<ip-address>|<ip-address/M>
[longer-prefixes]| cidr-only]
Function:
For displaying the routing messages permitted by BGP
Parameter: <ADDRESS-FAMILY>
: address-family such as “ipv4 unicast”
<ip-address>
: IP address
