Fully Operational Session

A

The correct answer is A. Established.

BGP (Border Gateway Protocol) is an exterior gateway protocol used for exchanging routing information between different autonomous systems (ASes) on the Internet. BGP establishes a TCP connection between two BGP peers and goes through several states before becoming fully operational.

The BGP states are as follows:

1. Idle: The initial state of a BGP connection where it is waiting for a start event, which could be either an administrative configuration or the initiation of a TCP session.

2. Connect: The BGP peer has initiated a TCP session with the remote peer, but BGP has not yet been established.

3. Active: The local router is trying to initiate a TCP session with the remote peer but has not yet received a response.

4. OpenSent: The local router has sent an OPEN message to the remote peer, but the BGP connection is not yet established.

5. OpenConfirm: The local router has received an OPEN message from the remote peer and is waiting for a KEEPALIVE message to confirm the establishment of the BGP connection.

6. Established: The BGP connection is fully operational, and both peers have exchanged their routing information.

Therefore, the correct answer is A. Established because it denotes a fully operational BGP session where both peers have exchanged their routing information. The other options, such as Active, Connect, and Operational, do not denote a fully operational BGP session.