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Configuring the AS_PATH attribute

Permitting local AS number to appear in routes from a peer or peer group

In general, BGP checks whether the AS_PATH attribute of a route from a peer contains the local AS

number. If yes, it discards the route to avoid routing loops.

In certain network environments (for example, a Hub&Spoke network in MPLS L3VPN), however,

the AS_PATH attribute of a route from a peer must be allowed to contain the local AS number.

Otherwise, the route cannot be advertised correctly.

To permit the local AS number to appear in routes from a peer or peer group and specify the

appearance times (IPv4):

Step Command Remarks

1. Enter system view.

system-view

N/A

2. Enter BGP view or BGP-VPN

instance view.

• Enter BGP view:

bgp as-number

• Enter BGP-VPN instance

view:

a. bgp as-number

b. ip vpn-instance

vpn-instance-name

N/A

3. Enter BGP IPv4 unicast

address family view or

BGP-VPN IPv4 unicast

address family view.

address-family ipv4

[

unicast

]

N/A

4. Permit the local AS number

to appear in routes from a

peer or peer group and

specify the appearance

times.

peer

{ group-name | ip-address

[ mask-length ] }

allow-as-loop

[ number ]

By default, the local AS number is

not allowed in routes from a peer

or peer group.

To permit the local AS number to appear in routes from a peer or peer group and specify the

appearance times (IPv6):