42. BGP common commands and matters needing attention

1. The route marked by r: IGP and BGP learn the same route, but the AD learned by IGP is smaller, so the route will mark that the route identified by r will not be put into the routing table, but will still be passed to other neighbors. The route identified by r can be viewed by the command show ip bgp rib-failure.

2. There are two ways to restart BGP:

Hard restart: clear ip bgp * disconnects TCP connection (clear ip bgp 2.2.2.2 for a neighbor)

Soft restart: clear ip bgp soft continues to TCP connection

3. Check the routes sent to neighbors

Show ip bgp neighbor 2.2.2.2 adveritsed-routes

4. Check the route sent by the neighbor

Show ip bgp neighbor 3.3.3.3 received-routes

By default, you cannot see the result after executing the above command. You need to execute neighbor 3.3.3.3 soft-reconfiguration inbound under the BGP routing process to allocate memory to save the route sent by the neighbor.

5 、 no auto-summary

Automatic summarization occurs when IGP routes are redistributed into BGP, and no auto-summary turns off automatic summarization under the BGP routing process, and the next hop and Metricvalue of the redistributed routes will be the same as before redistribution. This command is configured by default.