BGP Neighbor Status

There are six BGP Neighbor states.

Idle

The initial state of the BGP process. It starts the process of a TCP connection with the neighbor and moves to the Connect state.

Connect

Waiting for the TCP connection with the neighbor to be completed. If the TCP connection is successfully established, it sends a BGP OPEN message to switch to the OpenSent state. If it cannot establish a TCP connection, it switches to the Active state.

Active

It is trying to start the process of a TCP connection with the neighbor. If a TCP connection is successfully established, it sends an OPEN message and moves to the Open Sent state. If a TCP connection is made from the neighbor to an unexpected IP address, it stays in the Active state.

If you stay in the Active state, check your neighbor’s configuration as it is most likely a misconfiguration.

OpenSent

The OPEN message has been sent to the neighbor and is waiting for the neighbor to send an OPEN message. If there is an error, the NOTIFICATION message is sent and the state is Idle. If there are no errors, a KEEPALIVE message is sent and the hold time is negotiated. The AS number of the neighbor determines whether it is an IBGP neighbor or an EBGP neighbor, and the system moves to the OpenConfirm state.

OpenConfirm

It is waiting for a KEEPALIVE or NOTIFICATION message. If a KEEPALIVE or NOTIFICATION message is received, the system enters the established state; if a NOTIFICATION message is received, the system enters the idle state.

Established

BGP Neighbor is fully established. UPDATE messages can be exchanged while in the established state. The hold time is reset each time when a KEEPALIVE or UPDATE message is received. When the NOTIFICATION message is received, the state is moved to Idle.

How the BGP works