Forming a BGP Connection
BGP uses TCP/IP as its underlying transport and uses TCP port 179. BGP speakers transition through various states during the establishment of a neighbor relationship, as shown in Figure A-10.
Figure A-10. States in the Formation of a BGP Neighbor Relationship
The Idle state usually represents the condition in which BGP has not been enabled on the router, or a particular neighbor relationship has been shut down. When a connection is initiated through either router configuration or the removal of the shut-down state for a particular neighbor, BGP moves to the Connect state.
In the Connect state, BGP waits for a TCP connection ...
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