Users Guide

octet. By specifying the exactly number of bits in an IP address that belong to a prex list, the prex list can be used to aggregate
addresses and perform some functions; for example, redistribution.
You can use the following options to enable or disable the BFD session:
• Permit – The permit option enables creation of a BFD session on the specied prex list or prex list range. The no permit option
enables tear down of the BFD session if and only if the ACL has no permit entry that shares the same neighbor.
• Deny – The deny option prevents BFD sessions from getting created for the specied prex list or prex list range.
For more information on prex lists, see IP Prex Lists.
To enable BFD sessions on specic neighbors, perform the following steps:
Enter the following command to enable BFD session on specic next-hop neighbors:
CONFIGURATION
ip route bfd prefix-list prefix-list-name
The BFD session is established for the next-hop neighbors that are specied in the prex-list.
• The absence of a prex-list causes BFD sessions to be enabled on all the eligible next-hop neighbors.
• You can use only valid IPv4 unicast address prexes in the BFD prex list. An erroneous IP prex in a prex-list causes the entire prex-
list to be rejected.
• A BFD session is enabled for the directly connected next-hop neighbor specied in the congured destination prex list.
• If you attach an empty prex-list, all the existing established BFD sessions are teared down. If a destination prex or prex range is not
present in the prex-list, then it is considered as an implicit deny.
• When a destination prex is deleted from the prex-list using the no permit option, the corresponding BFD session is torn down
immediately. In this scenario, the BFD session tear down occurs only if the other destination prexes in the prex-list are not pointing to
the same neighbor.
• The permit option enables creation of a BFD session for the specied static destination prex or prex range. The system prevents
creation of BFD sessions for all other destination prexes that are explicitly specied as Deny in the prex list.
• If other destination prexes in the prex-list are pointing to the same neighbor, then the no permit or the deny option on a
particular destination prex neither creates a BFD session on a neighbor nor removes the static routes from the unicast database.
• BFD sessions created using any one IP prex list are active at any given point in time. If a new prex list is assigned, then BFD sessions
corresponding to the older (existing) prex list are replaced with the newer ones.
• Each time a prex list is modied, only addition or deletion of new entries in that prex list are processed for BFD session establishment
or tear down.
Changing Static Route Session Parameters
BFD sessions are congured with default intervals and a default role.
The parameters you can congure are: Desired TX Interval, Required Min RX Interval, Detection Multiplier, and system role. These
parameters are congured for all static routes. If you change a parameter, the change aects all sessions for static routes.
To change parameters for static route sessions, use the following command .
• Change parameters for all static route sessions.
CONFIGURATION mode
ip route bfd [prefix-list prefix-list-name] interval milliseconds min_rx milliseconds
multiplier value role [active | passive]
To view session parameters, use the show bfd neighbors detail command, as shown in the examples in Displaying BFD for BGP
Information
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Bidirectional Forwarding Detection (BFD)