Hi Ahmed,
In the OPENSENT and OPENCONFIRM states, the two peers are exchanging preliminary packets in order to establish their BGP session. If the exchanges are successful, the peers will enter the ESTABLISHED state. The peers must continue to exchange periodic KEEPALIVE packets to remain in the established state, unless the negotiated hold time is 0.
OpenSent State: BGP FSM listens for an Open message from its peer.
Once the message has been received, the router checks the validity of the Open message.
If there is an error it is because one of the fields in the Open message doesn’t match between the peers, e.g., BGP version mismatch, MD5 password mismatch, the peering router expects a different My AS, etc. The router then sends a Notification message to the peer indicating why the error occurred.
If there is no error, a Keepalive message is sent, various timers are set and the state is changed to OpenConfirm.
OpenConfirm State: The peer is listening for a Keepalive message from its peer.
If a Keepalive message is received and no timer has expired before reception of the Keepalive, BGP transitions to the Established state.
If a timer expires before a Keepalive message is received, or if an error condition occurs, the router transitions back to the Idle state
Following things to be checked;
1- Show tec brief all to see if we have tcp connection state.
2- Make sure you are using the correct ip address and autonomous sytem respectively on both the ends.
3- As you mentioned you are able to ping the neighbor ip address, does the bgp form neighbors directly (i.e I mean without source other inteface)?
If you are using other interface for example loopback to form neigbor , I belive you are using update source loopback0 command?
4- Troubleshooting BGP neighbors link:
http://meetings.ripe.net/ripe-44/presentations/ripe44-eof-bgp.pdf
http://www.informit.com/library/content.aspx?b=CCIE_Practical_Studies_II&seqNum=89
HTH
REgards
Inayath
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