Administrator Guide

BGP 1329
Dell Networking BGP supports manual start and stop events. A manual start
event occurs when the user first configures a peer (neighbor remote-as) or
administratively enables a peer (no neighbor shutdown). A manual stop event
occurs when the user administratively disables a neighbor (neighbor
shutdown).
Of the optional events in RFC 4271 section 8.1.2 - 8.1.5, the following events
are supported:
• AutomaticStart_with_DampPeerOscillations (Event 6)
• AutomaticStop (Event 8)
• IdleHoldTimer_Expires (Event 13)
When an attempt to establish an adjacency fails, Dell Networking puts the
adjacency in the IDLE state and starts the idle hold timer. When the idle
hold timer expires, Dell Networking moves the adjacency to the CONNECT
state and initiates a new TCP connection. If the neighbor does not respond to
the connection request, Dell Networking retries three times. The first retry is
done after the configured retry interval. Each subsequent retry doubles the
previous retry interval. So by default, the TCP connection is retried after 2, 4,
and 8 seconds. Configuring the initial retry interval to a large value can
prevent retries. The TCP stack times out a connection attempt in 20 seconds
(after retransmitting the SYN segment according to normal retransmit
procedures), sends a TCP reset, and notifies the application of the connection
failure. The connection failure resets the BGP connect retry timer, puts the
adjacency in IDLE state, and starts the idle hold timer.
Dell Networking BGP allows multiple BGP sessions between the same two
routers. However, each session must be established between different pairs of
IP addresses.
Dell Networking BGP includes two capabilities in every OPEN message it
sends. The first is the Route Refresh capability described in RFC 2918. The
second is the multiprotocol capability described in RFC 4760. Dell
Networking always advertises the IPv4/unicast AFI/SAFI pair. If the user has
activated IPv6 for the peer, the OPEN also includes the IPv6/unicast pair.
Even though Dell Networking BGP does not support any AFI/SAFI pairs
other than IPv4/unicast when IPv6 is not enabled, Dell Networking advertises
the multiprotocol capability with IPv4/unicast because some other
implementations appear to require this in order to establish an adjacency.