BGP active and passive peers
When a BGP peering takes place between two routers, one router takes the active role while the other takes the passive role. The router with the lowest BGP router identifier will be the active peer, and will actively search for, and establish the connection to the remote peer via TCP port 179. In this sense, the router with the lowest identifier will play the active role, while the other router will play the passive role.
This behavior can be changed by using the neighbor transport command with the appropriate keywords under the BGP configuration mode. For example, the following command will cause the local router to be the passive router in its BGP peering with neighbor 150.1.1.1:
neighbor 150.1.1.1 transport connection-mode passive
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