In which BGP state does the router wait for the TCP 3WHS handshake to complete?

In the BGP (Border Gateway Protocol) state machine, the state in which a router waits for the TCP three-way handshake (3WHS) to complete is known as the Connect state. During this phase, the router initiates a TCP connection to its BGP peer. It is essential for establishing a reliable transport layer connection before BGP can proceed with exchanging routing information.

When in the Connect state, the BGP implementation is actively monitoring the status of the TCP connection. If the three-way handshake is successful, the router transitions to the OpenSent state, in which it sends an OPEN message to the peer. If the TCP connection fails to establish or timeouts occur, the router may transition to the Active state, where it will attempt to re-establish the connection.

Understanding the different BGP states and their functions is critical for diagnosing routing problems and ensuring proper configuration of BGP sessions within the network.