Juniper JUNOSE, Configuration Manual

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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.
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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
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Use to enable BGP to detect whether a neighbor is unreachable by means of a
BFD protocol session to the neighbor.
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The peers in a BGP adjacency use the configured values to negotiate the actual
transmit intervals for BFD packets.
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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.
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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.
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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 the minimum receive interval and the minimum transmit
interval to the same value. The default value is 300 milliseconds.
■
You can use the multiplier keyword to specify the detection multiplier value.
The calculated BFD liveness detection interval can be different on each peer.
The multiplier value is roughly equivalent to the number of packets that can be
missed before the BFD session is declared to be down. The default value is 3.
■
For details on liveness detection negotiation, see JUNOSe IP Services Configuration
Guide .
142 ■
Detecting Peer Reachability with BFD
JUNOSe 11.0.x BGP and MPLS Configuration Guide