Configuring the BFD Protocol for RIP

The address bfd-liveness-detection command or the ip rip bfd-liveness-detection command configures the Bidirectional Forwarding Detection (BFD) protocol for RIP. The BFD protocol uses control packets and shorter detection time limits to more rapidly detect failures in a network. Also, because they are adjustable, you can modify the BFD timers for more or less aggressive failure detection.

Without BFD, when a RIP peer goes down, the routes learned from that peer are purged only after each route times out. The timeout is configurable with the timers invalid command. By default, the timeout is 180 seconds after each route was received or refreshed. Consequently routes are purged successively over varying time periods rather than all at once.

In contrast, when a BFD session exists between RIP peers, a peer that goes down is detected quickly. RIP simultaneously purges all routes learned from that peer and starts the hold-down timer for each peer.

When you issue the address bfd-liveness-detection command or the ip rip bfd-liveness-detection command on a RIP peer, the peer establishes BFD liveness detection with all BFD-enabled RIP peers. When the local peer receives an update from a remote RIP peer—if BFD is enabled and if the session is not already present—the local peer attempts to create a BFD session to the remote peer.

Each adjacent pair of peers negotiates an acceptable transmit interval for BFD packets. The negotiated value can be different on each peer. Each peer then calculates a BFD liveness detection interval. When a peer does not receive a BFD packet within the detection interval, it declares the BFD session to be down and purges all routes learned from the remote peer.

Note: Before the router can use the address bfd-liveness-detection command or the ip rip bfd-liveness-detection command, you must specify a BFD license key. To view an already configured license, use the show license bfd command.

For general information about configuring and monitoring the BFD protocol, see JUNOSe IP Services Configuration Guide.

address bfd-liveness-detection

ip rip bfd-liveness-detection

• Use to enable BFD (bidirectional forwarding detection) and define BFD values to more quickly detect RIP data path failures.
• Use the address bfd-liveness-detection command when you have used the address command to configure the RIP network. Use the ip rip bfd-liveness-detection command when you have used the network command to configure the RIP network.
• The peers in a RIP 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 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 .
• You can change the BFD liveness detection parameters at any time without stopping or restarting the existing session; BFD automatically adjusts to the new parameter value. However, no changes to BFD parameters take place until the values resynchronize with each peer.
• Example

  host1(config-if)#ip rip bfd-liveness-detection minimum-interval 800

  or

  host1(config-router)#address bfd-liveness-detection minimum-interval 800

• Use the no version to disable BFD on the RIP interface.
• See address bfd-liveness-detection
• See ip rip bfd-liveness-detection

Copyright © 2009, Juniper Networks, Inc. All rights reserved. Trademark Notice.