Configuring BFD for RIP

The Bidirectional Forwarding Detection (BFD) protocol is a simple hello mechanism that detects failures in a network. Hello packets are sent at a specified, regular interval. A neighbor failure is detected when the routing device stops receiving a reply after a specified interval. BFD works with a wide variety of network environments and topologies. BFD failure detection times are shorter than RIP detection times, providing faster reaction times to various kinds of failures in the network. These timers are also adaptive. For example, a timer can adapt to a higher value if the adjacency fails, or a neighbor can negotiate a higher value for a timer than the one configured.

Note: To enable BFD for RIP, both sides of the connection must receive an update message from the peer. By default, RIP does not export any routes. Therefore you must enable update messages to be sent by configuring an export policy for routes before a BFD session is triggered.

To enable failure detection, include the bfd-liveness-detection statement:

bfd-liveness-detection {detection-time {threshold milliseconds;}minimum-interval milliseconds;minimum-receive-interval milliseconds;multiplier number;no-adaptation;transmit-interval {threshold milliseconds;minimum-interval milliseconds;}version (1 | automatic);}

To specify the threshold for the adaptation of the detection time, include the threshold statement:

detection-time {threshold milliseconds;}

When the BFD session detection time adapts to a value equal to or higher than the threshold, a single trap and a system log message are sent.

To specify the minimum transmit and receive interval for failure detection, include the minimum-interval statement:

minimum-interval milliseconds;

This value represents the minimum interval at which the local routing device transmits hello packets as well as the minimum interval at which the routing device expects to receive a reply from a neighbor with which it has established a BFD session. You can configure a value in the range from 1 through 255,000 milliseconds. You can also specify the minimum transmit and receive intervals separately.

Note: Specifying an interval less than 300 ms can cause undesired BFD flapping.

To specify only the minimum receive intervals for failure detection, include the minimum-receive-interval statement:

minimum-receive-interval milliseconds;

This value represents the minimum interval at which the local routing device expects to receive a reply from a neighbor with which it has established a BFD session. You can configure a value in the range from 1 through 255,00 milliseconds.

To specify the number of hello packets not received by a neighbor that causes the originating interface to be declared down, include the multiplier statement:

multiplier number;

The default is 3, and you can configure a value in the range from 1 through 255.

To specify only the minimum transmit interval for failure detection, include the minimum-interval statement:

transmit-interval {minimum-interval milliseconds;}

This value represents the minimum interval at which the local routing device transmits hello packets to the neighbor with which it has established a BFD session. You can configure a value in the range from 1 through 255,000 milliseconds.

To specify the threshold for detecting the adaptation of the transmit interval, include the threshold statement:

transmit-interval {threshold milliseconds;}

The threshold value must be greater than the transmit interval.

To specify the BFD version used for detection, include the version statement:

version (1 | automatic);

The default is to have the version detected automatically.

You can trace BFD operations by including the traceoptions statement at the [edit protocols bfd] hierarchy level. For more information, see Tracing BFD Protocol Traffic.

In Junos OS Release 9.0 and later, you can configure BFD sessions not to adapt to changing network conditions. To disable BFD adaptation, include the no-adaptation statement:

no-adaptation;

Note: We recommend that you not disable BFD adaptation unless it is preferable not to have BFD adaptation enabled in your network.

For a list of hierarchy levels at which you can include these statements, see the statement summary sections for these statements.