peer allow-as-loop (BGP-VPN instance IPv4 address family view)

Function

The peer allow-as-loop command sets the number of local AS number repetitions.

The undo peer allow-as-loop command cancels the configuration.

By default, the local AS number cannot be repeated.

Format

peer ipv4-address allow-as-loop [ number ]

undo peer ipv4-address allow-as-loop

Parameters

Parameter	Description	Value
ipv4-address	Specifies the IPv4 address of a peer.	It is in dotted decimal notation.
number	Specifies the number of local AS number repetitions.	The value is an integer ranging from 1 to 10. The default value is 1.

Parameter

Description

Value

ipv4-address

Specifies the IPv4 address of a peer.

It is in dotted decimal notation.

number

Specifies the number of local AS number repetitions.

The value is an integer ranging from 1 to 10. The default value is 1.

Views

BGP-labeled VPN instance IPv4 address family view, BGP-VPN instance IPv4 address family view

Default Level

2: Configuration level

Task Name and Operations

Task Name	Operations
bgp	write

Usage Guidelines

Usage Scenario

BGP uses AS numbers to detect routing loops. The AS numbers in the AS_Path of each received route are matched against the local AS number configured using the bgp command and the fake AS number configured using the peer fake-as command. The largest number of times any of the configured AS numbers is repeated is considered as the maximum number. In the Hub and Spoke networking, if EBGP runs between a Hub-PE and a Hub-CE on a Hub site, the route sent from the Hub-PE to the Hub-CE carries the AS number of the Hub-PE. If the Hub-CE sends a routing update to the Hub-PE, the Hub-PE will deny it because the routing update contains the AS number of the Hub-PE.

To ensure proper route transmission in the Hub and Spoke networking, configure all the BGP peers on the path, along which the Hub-CE advertises private network routes to the Spoke-CE, to accept the routes in which the AS number repeats once.

Prerequisites

Peer relationships have been established using the peer as-number command.

Configuration Impact

If the peer allow-as-loop command is run for a peer multiple times, the latest configuration overrides the previous one.

Example

# Set the number of local AS number repetitions to 2.

<HUAWEI> system-view
[~HUAWEI] ip vpn-instance vpna
[*HUAWEI-vpn-instance-vpna] ipv4-family
[*HUAWEI-vpn-instance-vpna-af-ipv4] route-distinguisher 100:1
[*HUAWEI-vpn-instance-vpna-af-ipv4] quit
[*HUAWEI-vpn-instance-vpna] quit
[*HUAWEI] bgp 100
[*HUAWEI-bgp] ipv4-family vpn-instance vpna
[*HUAWEI-bgp-vpna] peer 1.1.1.1 as-number 100
[*HUAWEI-bgp-vpna] peer 1.1.1.1 allow-as-loop 2
<HUAWEI> system-view
[~HUAWEI] ip vpn-instance vpna
[*HUAWEI-vpn-instance-vpna] ipv4-family
[*HUAWEI-vpn-instance-vpna-af-ipv4] route-distinguisher 100:1
[*HUAWEI-vpn-instance-vpna-af-ipv4] quit
[*HUAWEI-vpn-instance-vpna] quit
[*HUAWEI] bgp 100
[*HUAWEI-bgp] vpn-instance vpna
[*HUAWEI-bgp-instance-vpna] peer 1.1.1.1 as-number 100
[*HUAWEI-bgp-instance-vpna] quit
[*HUAWEI-bgp] ipv4-labeled-unicast vpn-instance vpna
[*HUAWEI-bgp-labeled-vpna] peer 1.1.1.1 enable
[*HUAWEI-bgp-labeled-vpna] peer 1.1.1.1 allow-as-loop 2