Technical Tip : BGP Neighbor Adjacency States

[oarslan]

Description	This articles talks about BGP Neighbor Adjacency States.
Scope	FortiGate.
Solution	BGP establishes a TCP connection with peers, or adjacent routers. The Finite State Machine (FSM) is used by BGP to keep track of all BGP neighbors and their operational condition. The following states are possible for the BGP session to report: BGP States Idle : The BGP FSM's initial step is this. BGP recognizes a start event and attempts to establish a TCP connection with the BGP peer while simultaneously listening for a new connect from a peer router. Connect : Waiting for a successful three way handshake connection. Active : Unable to establish the TCP session. Open Sent : Waiting for an 'OPEN' message from the peer. Open Confirm : Waiting for the 'KEEP ALIVE' message from the peer. Established : Peers have successfully exchanged 'OPEN' and 'KEEP ALIVE' messages.