Deployment Guide

• 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 interval [prefix-list prefix-list-name] [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.
Disabling BFD for Static Routes
If you disable BFD, all static route BFD sessions are torn down.
A nal Admin Down packet is sent to all neighbors on the remote systems, and those neighbors change to the Down state.
To disable BFD for static routes, use the following command.
• Disable BFD for static routes.
CONFIGURATION mode
no ip route bfd
Congure BFD for OSPF
When using BFD with OSPF, the OSPF protocol registers with the BFD manager on the RPM.
BFD sessions are established with all neighboring interfaces participating in OSPF. If a neighboring interface fails, the BFD agent on the line
card noties the BFD manager, which in turn noties the OSPF protocol that a link state change occurred.
Conguring BFD for OSPF is a two-step process:
1 Enable BFD globally. Refer to Enabling BFD Globally.
2 Establish sessions with OSPF neighbors. Refer to Establishing Sessions with OSPF Neighbors.
Bidirectional Forwarding Detection (BFD)
147