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NLRI for this session: inet-unicast<br />

Peer supports Refresh capability (2)<br />

Table inet.0 Bit: 10000<br />

RIB State: BGP restart is complete<br />

Send state: in sync<br />

Active prefixes: 0<br />

Received prefixes: 0<br />

Suppressed due to damping: 0<br />

Advertised prefixes: 0<br />

Last traffic (seconds): Received 19 Sent 19 Checked 19<br />

Input messages: Total 12 Updates 0 Refreshes 0 Octets 254<br />

Output messages: Total 13 Updates 0 Refreshes 0 Octets 273<br />

Output Queue[0]: 0<br />

The third line of the output shows that the session has been established. The current<br />

state of the BGP connection is Established. If the connection isn’t up, but is in the<br />

process of establishing itself, this field shows the current state of the BGP session.<br />

These states correspond to the session establishment states defined in RFC 1771:<br />

Idle<br />

This is the initial stage of establishing a connection, when BGP is waiting for a<br />

start event.<br />

Connect<br />

BGP is waiting for TCP to establish its connection between the two peers.<br />

Active<br />

BGP is actively attempting to connect to its peer.<br />

OpenSent<br />

The local BGP peer has sent an open request to the peer and is waiting to receive<br />

an open message back.<br />

OpenConfirm<br />

BGP acknowledges that it has received an open message from the peer and is<br />

waiting to receive a keepalive message.<br />

When a BGP session doesn’t get established, the state often remains as Connect or<br />

Active. To troubleshoot the problem, use the show interfaces terse and show<br />

interfaces commands to check that the interfaces between the two routers are up<br />

and configured properly. Check the BGP configuration on both routers, making sure<br />

that the AS numbers are correct. Also, check the current state of the TCP session<br />

with the show system connections extensive command (see Recipe 13.3).<br />

The remainder of the third line and the next two lines provide additional information<br />

about the session. The Last State field shows the previous state of the BGP session,<br />

which is OpenConfirm, the BGP message the two peers exchange when they have<br />

confirmed that they will indeed establish a connection.<br />

Configuring a BGP Session Between Routers in Two ASs | 425<br />

This is the Title of the Book, eMatter Edition<br />

Copyright © 2008 O’Reilly & Associates, Inc. All rights reserved.

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