Users Guide

1404 BGP
BGP Finite State Machine (FSM)
Dell EMC Networking BGP supports all mandatory FSM session attributes
and the following optional session attributes (RFC 4271 section 8):
• AllowAutomaticStart — Connections are automatically restarted after an
error closes a connection. An adjacency to an external peer in the IDLE
state is automatically started if the routing interface to that peer comes up.
An adjacency to an internal peer in the IDLE state is automatically started
when the peer's IP address becomes reachable.
• AllowAutomaticStop — When a neighbor sends more prefixes than the
configured limit, the connection may be automatically shut down,
depending on configuration. AutoStop is also used for fast fallover. When
the routing interface to an external peer goes down, the peering session is
automatically stopped. Similarly, if an internal peer becomes unreachable,
the peering session is automatically stopped.
• CollisionDetectEstablishedState — When an OPEN message is received
on a TCP connection and the adjacency using that connection has already
reached ESTABLISHED state, the adjacency is cleared. If an OPEN
message is received on a different TCP connection than the one used to
reach ESTABLISHED state, the new TCP connection is cleared and the
adjacency remains up.
• DampPeerOscillations — An idle hold time is enforced between automatic
restarts. The length of the idle time depends on the reason the adjacency
entered the idle state.
• IdleHoldTime/IdleHoldTimer — After an error clears a connection or a
TCP connection fails, Dell EMC Networking BGP waits before
attempting to reestablish the adjacency. The waiting time varies
depending on the event. When a TCP connection fails, BGP waits 30 to 60
seconds. When a NOTIFICATION is received, BGP waits 1 to 2 seconds.
Other events trigger a wait of 10 to 20 seconds. The delay time is not
configurable.
• SendNOTIFICATIONWithoutOPEN — Dell EMC Networking will
accept a NOTIFICATION packet from a peer that has not first sent an
OPEN packet. Dell EMC Networking will not send a NOTIFICATION
without first sending an OPEN.
None of the optional session attributes are configurable.