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detection-time (BFD Liveness Detection)

 

Syntax

BGP

EVPN, L2VPN, VPLS

Release Information

Statement introduced in Junos OS Release 8.2.

Support for BFD authentication introduced in Junos OS Release 9.6.

Description

Enable BFD failure detection. The BFD failure detection timers are adaptive and can be adjusted to be faster or slower. The lower the BFD failure detection timer value, the faster the failure detection and vice versa. For example, the timers can adapt to a higher value if the adjacency fails (that is, the timer detects failures more slowly). Or a neighbor can negotiate a higher value for a timer than the configured value. The timers adapt to a higher value when a BFD session flap occurs more than three times in a span of 15 seconds. A back-off algorithm increases the receive (Rx) interval by two if the local BFD instance is the reason for the session flap. The transmission (Tx) interval is increased by two if the remote BFD instance is the reason for the session flap. You can use the clear bfd adaptation command to return BFD interval timers to their configured values. The clear bfd adaptation command is hitless, meaning that the command does not affect traffic flow on the routing device.

Starting in Junos OS Release 20.3R1, we’ve introduced distributed mode for BFD failure detection. The distributed mode provides faster BFD failure detection of 300 (3 x 100) ms. You can enable distributed mode when you configure the BFD failure detection timer value less than 500 ms.

For optimization and performance enhancement, you must configure the BFD failure detection timer value in multiples of 50 ms.

Options

threshold millisecondsSpecify the threshold for the adaptation of the BFD session detection time. When the detection time adapts to a value equal to or greater than the threshold, a single trap and a single system log message are sent.
Note

The threshold value must be equal to or greater than the transmit interval.

The threshold time must be equal to or greater than the value specified in the minimum-interval or the minimum-receive-interval statement.

Range: 1 through 255,000 milliseconds

Required Privilege Level

routing—To view this statement in the configuration.

routing-control—To add this statement to the configuration.