BGP - FSM - Connect State

Like all dynamic routing protocols, BGP employs a Finite State Machine (FSM) to establish and maintain peerings between BGP routers, and to exchange routing information.

Within this FSM, we have the Connect state. In the Connect state, the router begins an initial TCP three-way handshake and is waiting for an acknowledgment of the TCP connection request (SYN packet) it has sent to its neighbor. If the router gets an acknowledgment (SYN-ACK packet), it moves to the OpenSent state. If it does not receive an acknowledgment, it will keep trying until the ConnectRetry timer expires, and then it will move to the Active state. The Connect state is an adjacency state that a BGP peering goes into when the initial Connect state fails.

Links

https://networklessons.com/bgp/bgp-neighbor-adjacency-states/