nexthop recursive-lookup restrain (BGP view)

Function

The nexthop recursive-lookup restrain command configures the intervals for increasing, retaining, and clearing the penalty value for BGP recursion suppression in case of next hop flapping.

The undo nexthop recursive-lookup restrain command restores the default configuration.

By default, the intervals for increasing, retaining, and clearing the penalty value for BGP recursion suppression in case of next hop flapping are 60s, 120s, and 600s, respectively.

Format

nexthop recursive-lookup restrain suppress-interval add-count-time hold-interval hold-count-time clear-interval clear-count-time

undo nexthop recursive-lookup restrain suppress-interval hold-interval clear-interval

Parameters

Parameter	Description	Value
hold-interval hold-count-time	Specifies the interval for retaining the penalty value for recursion suppression.	The value is an integer ranging from 1 to 65535, in seconds. The default values is recommended.
clear-interval clear-count-time	Specifies the interval for clearing the penalty value for recursion suppression.	The value is an integer ranging from 1 to 65535, in seconds. The default values is recommended.
suppress-interval add-count-time	Specifies the interval for increasing the penalty value for recursion suppression.	The value is an integer ranging from 1 to 65535, in seconds. The default value is recommended.

Parameter

Description

Value

hold-interval hold-count-time

Specifies the interval for retaining the penalty value for recursion suppression.

The value is an integer ranging from 1 to 65535, in seconds. The default values is recommended.

clear-interval clear-count-time

Specifies the interval for clearing the penalty value for recursion suppression.

The value is an integer ranging from 1 to 65535, in seconds. The default values is recommended.

suppress-interval add-count-time

Specifies the interval for increasing the penalty value for recursion suppression.

The value is an integer ranging from 1 to 65535, in seconds. The default value is recommended.

Views

BGP view

Default Level

2: Configuration level

Task Name and Operations

Task Name	Operations
bgp	write

Usage Guidelines

Usage Scenario

If a large number of routes recurse to the same next hop that flaps frequently, the system will be busy processing changes of these routes, which consumes excessive system resources and leads to high CPU usage. To address this problem, configure BGP recursion suppression in case of next hop flapping.

After this function is enabled, BGP calculates the penalty value that starts from 0 by comparing the flapping interval with configured intervals if next hop flapping occurs. When the penalty value exceeds 10, BGP suppresses route recursion to the corresponding next hop. For example, if the intervals for increasing, retaining, and clearing the penalty value are T1, T2, and T3, respectively, BGP calculates the penalty value as follows:

Increases the penalty value by 1 if the flapping interval is less than T1.
Retains the penalty value if the flapping interval is greater than or equal to T1, but less than T2.
Reduces the penalty value by 1 if the flapping interval is greater than or equal to T2, but less than T3.
Clears the penalty value if the flapping interval is greater than or equal to T3.
To configure the intervals for increasing, retaining, and clearing the penalty value for BGP recursion suppression in case of next hop flapping, run the nexthop recursive-lookup restrain command.

Precautions

Currently, the maximum interval for increasing the penalty value for recursion suppression is 20.

If the intervals for increasing, retaining, and clearing the penalty value are T1, T2, and T3, respectively, the relationship between them is T1 < T2 < T3.

Example

# Set the intervals for increasing, retaining, and clearing the penalty value for BGP recursion suppression in case of next hop flapping to 30s, 60s, and 120s, respectively.

<HUAWEI> system-view
[~HUAWEI] bgp 100
[*HUAWEI-bgp] nexthop recursive-lookup restrain suppress-interval 30 hold-interval 60 clear-interval 120