check-first-as (BGP multi-instance view)

Function

The check-first-as command enables BGP to check the first AS number in the AS_Path that is carried in Update messages sent by EBGP peers.

The undo check-first-as command disables the function.

By default, the function is enabled.

Format

check-first-as

undo check-first-as

Parameters

None

Views

BGP multi-instance view

Default Level

2: Configuration level

Task Name and Operations

Task Name	Operations
bgp	write

Usage Guidelines

Usage Scenario

By default, BGP checks the first AS number in the AS_Path that is carried in Update messages sent by EBGP peers. The Update messages are accepted only when the first AS number is the AS where the EBGP peers locate. Otherwise, the Update messages are denied.

Follow-up Procedure

Run the refresh bgp command if you want to check the received routes again.

Precautions

The check-first-as command is not listed in the configuration file.

After the undo check-first-as command is configured, routing loops may occur. Therefore, exercise caution when running the command.

Example

# Check the first AS number in the AS_Path list that is carried in the Update messages sent by EBGP peers.

<HUAWEI> system-view
[~HUAWEI] bgp 100 instance a
[*HUAWEI-bgp-instance-a] check-first-as