Juniper IGP - CONFIGURATION GUIDE V11.1.X, Configuration Manual

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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
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Use to enable BFD (bidirectional forwarding detection) and define BFD values
to more quickly detect RIP data path failures.
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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.
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The peers in a RIP 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.
Configuring the BFD Protocol for RIP
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Chapter 4: Configuring RIP