When you configure BFD for a BGP session, the normal BGP keepalive mechanism is not
disabled. Unless you configure BGP not to do so, BGP still sends keepalive messages
and brings the BGP session down if the holdtimer expires.
When you configure this feature, BGP requests BFD to start a BFD protocol session as
soon as the BGP session enters the established state. BGP allows the BFD protocol
session to come up only when the source address of received BFD packets matches the
destination address of the BGP neighbor. When the BFD protocol session comes up, BGP
logs this event and reports the session in subsequent show commands. If the BFD protocol
session goes down, BGP immediately brings down the BGP session and takes all
associated actions.
Whenever a BGP session leaves the established state, BGP requests BFD to stop the
BFD protocol session. BGP also requests BFD to bring the BFD protocol session down
and inform BGP if the local interface goes down.
To enable a BGP session to come up even if the remote peer does not support BFD or
has not been configured to use BFD, the following behavior applies:
•
The BGP session can come up when the BFD protocol session is not yet up.
•
The BGP session can stay up even when the BFD protocol session never comes up.
You can specify a desired rate for receiving BFD packets from the peer, transmitting them
to the peer, or both, by setting a desired time interval between the packets. The actual
timer values can be different as a result of other applications requesting BFD protocol
sessions on the same interface with different timer values, as a result of timer value
negotiation between the local and remote BFD speakers, or both.
In the following example, the router is configured to send BFD packets to peer 10.25.43.1
with a minimum interval of 450 milliseconds between the packets, and to accept BFD
packets from the peer only with the same minimum interval:
host1(config)#router bgp 100
host1(config-router)#neighbor 10.25.43.1 bfd-liveness-detection minimum-interval 450
neighbor bfd-liveness-detection
• Use to enable BGP to detect whether a neighbor is unreachable by means of a BFD
protocol session to the neighbor.
• The peers in a BGP adjacency use the configured values to negotiate the actual transmit
intervals for BFD packets.
• You can use the minimum-transmit-interval keyword to specify the interval at which
the local peer proposes to transmit BFD control packets to the remote peer. The
default value is 300 milliseconds.
• You can use the minimum-receive-interval keyword to specify the minimum interval
at which the local peer must receive BFD control packets from the remote peer. The
default value is 300 milliseconds.
• You can use the minimum-interval keyword to specify the same value for both of
those intervals. Configuring a minimum interval has the same effect as configuring
139Copyright © 2010, Juniper Networks, Inc.
Chapter 1: Configuring BGP Routing
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