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CLI-based Configuration Guide - Reliability

AR100-S, AR110-S, AR120-S, AR150-S, AR160-S, AR200-S, AR1200-S, AR2200-S, and AR3200-S V200R009

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Configuring BFD Session Flapping Suppression

Configuring BFD Session Flapping Suppression

Usage Scenario

If link quality is poor, BFD results in frequent service switchover. You can configure link flapping times to prevent frequent service switchover, protecting link resources and reducing link resource consumption.

Do not configure both the dampening timer-interval and wtr commands. Otherwise, the BFD session recovery period becomes long.

Procedure

  1. Run system-view

    The system view is displayed.

  2. Run bfd

    The BFD session view is displayed.

  3. Run dampening timer-interval maximum maximum-milliseconds initial initial-milliseconds secondary secondary-milliseconds

    BFD session flapping suppression timers are configured.

    BFD session flapping suppression timers start by default. The default initial, secondary, and maximum BFD session flapping suppression timer values are 2000 ms, 5000 ms, and 12000 ms, respectively.

    After the dampening timer-interval command is run:

    1. When a BFD session flaps for the first time, the initial BFD session flapping suppression timer starts. If the BFD session flaps again before the initial BFD session flapping suppression timer expires, BFD session renegotiation is triggered after the initial BFD session flapping suppression timer expires.
    2. After the initial BFD session flapping suppression timer ends, the secondary BFD session flapping suppression timer starts. If the BFD session flaps before the secondary BFD session flapping suppression timer expires, BFD session renegotiation is triggered after the secondary BFD session flapping suppression timer expires. After that, the timer value is secondary-milliseconds x 2(n-1), where n is the number of times that the secondary BFD session flapping suppression timer starts.
    3. After the timer value of secondary-milliseconds x 2(n-1) is greater than or equal to the value specified by maximum-milliseconds, the BFD session uses the value specified by maximum-milliseconds as a flapping delay three consecutive times. After that, the BFD session flapping delay is recalculated based on Step 1.
    When BFD session flapping suppression is enabled, the punishment rules for BFD session flapping suppression are as follows:
    1. Each time a BFD session enters the fault-triggered Down state, the punishment value of the BFD session increases by 20 (a maximum of 240 is allowed).
    2. Each time a BFD session remains 1s in the Up state, the punishment value of the BFD session decreases by 1.
    3. If the punishment value of a BFD session exceeds 45, set a flapping suppression interval for the BFD session to twice the value of maximum maximum-milliseconds configured using the dampening timer-interval maximum maximum-milliseconds initial initial-milliseconds secondary secondary-milliseconds command. If the punishment value of a BFD session exceeds 90, set a flapping suppression interval for the BFD session to four times the value of maximum maximum-milliseconds. If the punishment value of a BFD session exceeds 135, set a flapping suppression interval for the BFD session to eight times the value of maximum maximum-milliseconds. If the punishment value of a BFD session exceeds 180, set a flapping suppression interval for the BFD session to sixteen times the value of maximum maximum-milliseconds.
    4. If a BFD session is suppressed by an intelligent timer, the punishment value of the BFD session increases/decreases based only on rules a and b. The BFD session does not enter the punishment suppression state, that is, rule c does not take effect. Rule c takes effect only if suppression by the intelligent timer ends.
    NOTE:

    The configured maximum BFD session flapping suppression timer value must be greater than the configured initial or secondary BFD session flapping suppression timer value. Otherwise, the configuration fails.

    By default, BFD session flapping suppression is enabled. To allow the system to immediately start the next negotiation after a BFD session goes Down (excluding AdminDown), run the session-damping disable command to disable BFD session flapping suppression.

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Updated: 2019-05-17

Document ID: EDOC1000174116

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