bgp fast-refresh enable

Function

The bgp fast-refresh enable command enables the BGP Prefix Independent Convergence (PIC) function.

The undo bgp fast-refresh enable command disables the BGP PIC function.

By default, the BGP PIC function is enabled on the switch.

Product	Support
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	Supported
S2720-EI, S5720I-SI, S5720-LI, S5735-L, S5735S-L, S5735S-L-M, S5720S-LI, S5720S-SI, S5720-SI, S5735-S, S5735S-S, S5735-S-I, S5730S-EI, S5730-SI, S6720-LI, S6720S-LI, S6720S-SI, and S6720-SI	Not supported

Format

bgp fast-refresh enable

undo bgp fast-refresh enable

Parameters

None

Views

System view

Default Level

2: Configuration level

Usage Guidelines

Usage Scenario

When there are primary and backup paths for a BGP route, and a fault occurs on the primary path, the route must be updated and traffic must be switched to the backup path as soon as possible. This process is called BGP route convergence. As the network expands in scale and route prefixes, the BGP route convergence speed is affected by the number of route prefixes. More route prefixes indicate slower route convergence speed. If a network fault occurs, many packets are lost due to the slow route convergence speed. This can have a large impact on some services that are sensitive to packet loss. BGP PIC is also called BGP fast refresh. It indicates that the BGP route convergence speed is independent of the number of route prefixes. After this function is enabled, the BGP route convergence speed becomes faster without being affected by the number of route prefixes. This function reduces data loss during route convergence. When this function becomes unavailable, you can run the undo bgp fast-refresh enable command to disable it. BGP routes are then converged as usual; however, the route convergence speed is slow.

Precautions

Only IBGP routes support the BGP PIC function, and VPN routes do not support this function.
If the BGP load balancing (ECMP) or BGP Auto FRR function has been configured on the device or the next hop of a BGP route is iterated to a tunnel interface, the BGP PIC function does not take effect.
Disabling the BGP PIC function requires the device to be restarted after the configuration is saved or requires all BGP ASs to be reset. Otherwise, disabling the BGP PIC function takes effect only for the subsequently generated routing tables.

Enabling the BGP PIC function requires the device to be restarted.

Example

# Disable the BGP PIC function on the switch.

<HUAWEI> system-view
[HUAWEI] undo bgp fast-refresh enable
Warning: The operation will take effect only on routing tables generated later. 
Please save configuration and reboot this device or reset all BGP ASs after this
 operation.