Cisco Catalyst 4500 Series - Configuring BFD Echo Mode

40-15
Catalyst 4500 Series Switch, Cisco IOS Software Configuration Guide - Cisco IOS XE 3.9.xE and IOS 15.2(5)Ex
Chapter 40 Configuring Bidirection Forwarding Detection
How to Configure 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 switches.
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, 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 on page 40-8 for more information.
Restrictions
BFD echo mode which is supported in BFD Version 1.
This section contains the following configuration tasks for BFD echo mode:
• Configuring the BFD Slow Timer, page 40-16
• Disabling BFD Echo Mode Without Asymmetry, page 40-16
Note 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.
Step 12
show ip static route bfd
Example:
Switch# show ip static route bfd
(Optional) Displays information about the static BFD
configuration from the configured BFD groups and
nongroup entries.
Step 13
exit
Example:
Switch# exit
Exits privileged EXEC mode and returns to user EXEC
mode.
Command or Action Purpose