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.
Configuring the BFD Protocol for RIP
■
225
Chapter 4: Configuring RIP
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