Routing Configuration Guide for Cisco 8000 Series Routers, Cisco IOS XR Release

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BFD echo mode

Updated: June 30, 2026

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Describes how BFD echo mode uses fast-rate echo packets on physical interfaces to improve link failure detection, while noting default behavior and session-scale limitations for IPv4 single-hop deployments.

BFD echo mode is a diagnostic mechanism that

  • improves link failure detection by sending echo packets at fast rates

  • sends echo packets more frequently than control packets to detect link failures, and

  • is enabled by default for IPv4 on physical interfaces with a minimum interval of less than 3 seconds.

Table 1. Feature History Table

Feature Name

Release

Feature Description

BFD echo mode

Release 25.4.1

Introduced in this release on: Fixed Systems (8700 [ASIC: K100])(select variants only*)

*This feature is supported on Cisco 8711-48Z-M routers.

BFD echo mode

Release 25.1.1

Introduced in this release on: Fixed Systems (8700 [ASIC: K100], 8010 [ASIC: A100])(select variants only*)

*This feature is supported on:

  • 8712-MOD-M

  • 8011-4G24Y4H-I

BFD echo mode

Release 24.4.1

Introduced in this release on: Fixed Systems (8200 [ASIC: P100], 8700 [ASIC: P100])(select variants only*); Modular Systems (8800 [LC ASIC: P100])(select variants only*)

*This feature is supported on:

  • 8212-48FH-M

  • 8711-32FH-M

  • 88-LC1-36EH

  • 88-LC1-12TH24FH-E

  • 88-LC1-52Y8H-EM
Note

If you enable BFD echo mode for IPv4, the maximum number of supported BFDv4 single-hop sessions drops by 50%. This limit does not apply to BFDv6 sessions or BFDv4 multihop sessions.

If you configured a BFD minimum interval greater than three seconds on a physical interface by using the bfd minimum-interval command, change the interval to less than three seconds before you enable echo mode. This requirement does not apply to bundle member links because they always support echo mode.

Override the default echo packet source address

You can override the default IP source address for BFD echo packets globally on the router or for a specific interface.

If you do not specify an echo packet source address, BFD uses the IP address of the output interface as the default source address for an echo packet.

You can use the echo ipv4 source command in BFD or interface BFD configuration mode to specify the IP address that you want to use as the echo packet source address.

Configure echo packet source address globally for BFD

Procedure

1.

Enter BFD configuration mode.

Example:

Router(config)# bfd
2.

Configure the IPv4 source address for BFD echo packets in the 32-bit IP address in dotted-decimal format (A.B.C.D).

Example:

Router(config-bfd)# echo ipv4 source 10.10.10.1
Router(config-bfd)# commit

Configure echo packet source address on an interface

Procedure

1.

Enter BFD configuration mode.

Example:

Router# configure
Router(config)# bfd
2.

Enter BFD interface configuration mode for a specific interface. In BFD interface configuration mode, you can specify an IPv4 address of an individual interface.

Example:

Router(config-bfd)# interface HundredGige 0/1/5/0
3.

Configure an IPv4 address to be used as the source address in BFD echo packets in the 32-bit IP address in dotted-decimal format (A.B.C.D).

Example:

Router(config-bfd-if)# echo ipv4 source 10.10.10.1
Router(config-bfd-if)# commit

Disable echo mode

Disable BFD echo mode for BFP on the router or on a specific interface when the environment does not support echo-mode operation.

  • BFD does not support asynchronous operation in echo mode in certain environments.

  • You can disable echo mode for BFD on the entire router, or for a particular interface.

Disable echo mode globally

This task describes how to disable echo mode for BFD on a router.

Procedure

1.

Enter BFD configuration mode.

Example:

Router# configure
Router(config)# bfd
2.

Run the echo disable command to disable echo mode on the router.

Example:

Router(config-bfd)# echo disable
Router(config-bfd)# commit

Disable echo mode on an interface

This task describes how to disable echo mode for BFD on an interface.

Procedure

1.

Enter BFD configuration mode.

Example:

Router# configure
Router(config)# bfd
2.

Enter BFD interface configuration mode for a specific interface.

Example:

Router(config-bfd)# interface HundredGige 0/1/5/0

In BFD interface configuration mode, you can disable echo mode on an individual interface.
3.

Run the echo disable command to disable echo mode on the router.

Example:

Router(config-bfd-if)# echo disable
Router(config-bfd-if)# commit