Configuring Bfd Echo Mode - Cisco Catalyst 9500 series Configuration Manual

Configuring Bidirectional Forwarding Detection

Configuring BFD Echo Mode

BFD echo mode is enabled by default, but you can disable it such that it can run independently in each direction.
BFD echo mode works with asynchronous BFD. Echo packets are sent by the forwarding engine and forwarded
back along the same path in order to perform detection--the BFD session at the other end does not participate
in the actual forwarding of the echo packets. The echo function and the forwarding engine are responsible for
the detection process; therefore, the number of BFD control packets that are sent out between two BFD
neighbors is reduced. In addition, because the forwarding engine is testing the forwarding path on the remote
(neighbor) system without involving the remote system, there is an opportunity to improve the interpacket
delay variance, thereby achieving quicker failure detection times than when using BFD Version 0 with BFD
control packets for the BFD session.
Echo mode is described as without asymmetry when it is running on both sides (both BFD neighbors are
running echo mode).
Prerequisites
BFD must be running on all participating routers.
Before using BFD echo mode, you must disable the sending of Internet Control Message Protocol (ICMP)
redirect messages by entering the no ip redirects command, in order to avoid high CPU utilization.
The baseline parameters for BFD sessions on the interfaces over which you want to run BFD sessions to BFD
neighbors must be configured. See the Configuring BFD Session Parameters on the Interface section for more
information.
Restrictions
BFD echo mode does not work in conjunction with Unicast Reverse Path Forwarding (uRPF) configuration.
If BFD echo mode and uRPF configurations are enabled, then the sessions will flap.
Disabling BFD Echo Mode Without Asymmetry
The steps in this procedure show how to disable BFD echo mode without asymmetry—no echo packets will
be sent by the router, and the router will not forward BFD echo packets that are received from any neighbor
routers.
Repeat the steps in this procedure for each BFD router.
Procedure
Step 1
Command or Action
enable
Example:
Router> enable
Routing Configuration Guide, Cisco IOS XE Everest 16.6.x (Catalyst 9500 Switches)
How to Configure Bidirectional Forwarding Detection
Purpose
Enables privileged EXEC mode.
• Enter your password if prompted.
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