session-damping disable

Function

The session-damping disable command disables BFD session flapping suppression.

The undo session-damping disable command enables BFD session flapping suppression.

By default, BFD session flapping suppression is enabled.

Only the S5720-EI, S5720-HI, S5730-HI, S5731-H, S5731-S, S5731S-H, S5731S-S, S5732-H, S6720-EI, S6720-HI, S6720S-EI, S6730-H, S6730S-H, S6730-S, and S6730S-S support this command.

Format

session-damping disable

undo session-damping disable

Parameters

None

Views

BFD view

Default Level

2: Configuration level

Usage Guidelines

Usage Scenario

If a BFD session frequently flaps, frequent link switchovers may occur, which results in packet loss. If multiple BFD sessions frequently flap on a device within a certain time, many device resources are consumed. When BFD session flapping suppression is enabled, the system establishes a more intelligent punishment mechanism for each BFD session, properly reducing the establishment of the BFD session. The system also periodically checks the flapping of all BFD sessions on the device, and more strictly suppresses the sessions with the most frequent flapping if necessary.

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.

Precautions

When BFD session flapping suppression is enabled, the device can adjust the flapping suppression time based on the penalty value in addition to the value of the intelligent timer (dampening timer-interval). The penalty value is adjusted as follows:

When a BFD session goes Down each time, the penalty value of the BFD session increases by 20. The initial value is 0 and the maximum penalty value is 240.
When a BFD session keeps Up for 1s each time, the penalty value decreases by 1. The minimum penalty value is 0.
If the penalty value of a BFD session exceeds 45, the flapping suppression time is twice (that is, 2¹) the value of maximum-milliseconds. If the penalty value of a BFD session exceeds 90, the flapping suppression time is four times (that is, 2²) the value of maximum-milliseconds, and so on. The maximum-milliseconds is configured using the dampening timer-interval command.
If a BFD session is suppressed by the intelligent timer, the penalty value is adjusted based on rules 1 and 2 and the BFD session does not enter the penalty suppression state. That is, rule 3 does not take effect. Rule 3 takes effect only when suppression by the intelligent timer ends.

When multiple BFD sessions exist on the device, the penalty value is adjusted considering Down events of all BFD sessions in a period of time.

The session-damping disable command takes effect for all types of BFD sessions.

Example

# Disable BFD session flapping suppression.

<HUAWEI> system-view
[HUAWEI] bfd
[HUAWEI-bfd] session-damping disable