BFD Dampening

The BFD Dampening feature introduces a configurable exponential delay mechanism to suppress the excessive effect of remote node reachability events flapping with Bidirectional Forwarding Detection (BFD). The BFD Dampening feature allows the network operator to automatically dampen a given BFD session to prevent excessive notification to the BFD clients, thus preventing unnecessary instability in the network. Configuring the BFD Dampening feature on a high-speed interface with routing clients improves the convergence time and stability throughout the network.

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Information About BFD Dampening

Overview of BFD Dampening

Bidirectional Forwarding Detection (BFD) is a mechanism used by the routing protocols to quickly realize the reachability failures to their neighbors. When BFD detects a reachability status change of a neighbor, clients are notified immediately. Sometimes it might be critical to minimize changes in routing tables so as not to impact convergence, in case of any micro failure. An unstable link that flaps excessively can cause other devices in the network to consume substantial system processing resources, and it can cause routing protocols to lose synchronization with the state of the flapping link.

The BFD Dampening feature introduces a configurable exponential delay mechanism to suppress the excessive effect of remote node reachability events flapping with BFD. The BFD Dampening feature allows the network operator to automatically dampen a given BFD session to prevent excessive notification to the BFD clients, thus preventing unnecessary instability in the network. Dampening the notification to a BFD client suppresses BFD notification until the session under monitoring stops flapping and becomes stable.

Configuring the BFD Dampening feature, especially on a high-speed interface with routing clients, improves the convergence time and stability throughout the network. BFD dampening can be applied to all types of BFD sessions, including IPv4/single-hop/multihop, Multiprotocol Label Switching-Transport Profile (MPLS-TP), and Pseudo Wire (PW) Virtual Circuit Connection Verification (VCCV).

You can configure the BFD Dampening feature at the BFD template level (both single-hop and multihop templates). Dampening is applied to all the sessions that use the BFD template. If you do not want a session to be dampened, you should use a new BFD template without dampening for the new session. By default, the dampening functionality is not enabled on a template.

How to Configure BFD Dampening

Configuring BFD Dampening

SUMMARY STEPS

    1.    enable

    2.    configure terminal

    3.    bfd-template multi-hop template-name

    4.    interval min-tx milliseconds min-rx milliseconds multiplier multiplier-value

    5.    dampening [ half-life-period reuse-threshold suppress-threshold max-suppress-time]

    6.    end

    7.    show bfd neighbors details

    8.    show bfd neighbors dampening

    9.    show bfd neighbors dampened


DETAILED STEPS
     Command or ActionPurpose
    Step 1 enable


    Example:
    Device> enable
     

    Enables privileged EXEC mode.

    • Enter your password if prompted.

     
    Step 2 configure terminal


    Example:
    Device# configure terminal
     

    Enters global configuration mode.

     
    Step 3 bfd-template multi-hop template-name


    Example:
    Device(config)# bfd-template multi-hop doctemplate
     

    Creates a Bidirectional Forwarding Detection (BFD) template and enters BFD configuration mode.

     
    Step 4 interval min-tx milliseconds min-rx milliseconds multiplier multiplier-value


    Example:
    Device(config-bfd)# interval min-tx 120 min-rx 100 multiplier 3
     

    Configures the transmit and receive intervals between BFD packets, and specifies the number of consecutive BFD control packets that must be missed before BFD declares that a peer is unavailable.

     
    Step 5 dampening [ half-life-period reuse-threshold suppress-threshold max-suppress-time]


    Example:
    Device(config-bfd)# dampening 2 1000 3000 8
     

    Configures a device to dampen a flapping session.

     
    Step 6 end


    Example:
    Device(config-bfd)# end
     

    Exits BFD configuration mode and returns to privileged EXEC mode.

     
    Step 7 show bfd neighbors details


    Example:
    Device# show bfd neighbors details
     

    (Optional) Displays the listing of existing BFD adjacencies and the dampening information about the BFD sessions if BFD dampening is enabled for the session.

     
    Step 8 show bfd neighbors dampening


    Example:
    Device# show bfd neighbors dampening
     

    (Optional) Displays the dampening information about the BFD sessions configured with BFD dampening.

     
    Step 9 show bfd neighbors dampened


    Example:
    Device# show bfd neighbors dampened
     

    (Optional) Displays the dampening information about the BFD sessions that are currently dampened.

     

    Configuration Examples for BFD Dampening

    Example: Configuring BFD Dampening

    The following example shows how to configure BFD dampening. 

    bfd-template multi-hop doctemplate
 interval min-tx 120 min-rx 100 multiplier 3
 dampening 2 1000 3000 8

    Additional References for BFD Dampening

    Related Documents

    Related Topic

    Document Title

    Cisco IOS commands

    Cisco IOS Master Command List, All Releases

    BFD commands

    Cisco IOS IP Routing: Protocol-Independent Command Reference

    Bidirectional Forwarding Detection

    IP Routing BFD Configuration Guide

    Technical Assistance

    Description

    Link

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    http:/​/​www.cisco.com/​cisco/​web/​support/​index.html

    Feature Information for BFD Dampening

    The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.

    Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to . An account on Cisco.com is not required.
    Table 1 Feature Information for BFD Dampening

    Feature Name

    Releases

    Feature Information

    BFD Dampening

    Cisco IOS XE Release 3.8S

    Cisco IOS Release 15.3(2)T

    The BFD Dampening feature introduces a configurable exponential delay mechanism to suppress the excessive effect of remote node reachability events flapping with BFD. This feature also allows the network operator to automatically dampen a given BFD session to prevent excessive notification to the BFD clients, thus preventing unnecessary instability in the network.

    The following commands were introduced or modified: dampening (bfd) and show bfd neighbors.