HP 5920 Series Command Reference Manual page 355

Syntax
In BGP IPv4 unicast address family view/BGP-VPN IPv4 unicast address family view/BGP VPNv4
address family view/BGP L2VPN address family view:
peer { group-name | ip-address } allow-as-loop [ number ]
undo peer { group-name | ip-address } allow-as-loop
In BGP IPv6 unicast address family view:
peer { group-name | ip-address | ipv6-address } allow-as-loop [ number ]
undo peer { group-name | ip-address | ipv6-address } allow-as-loop
In BGP VPN IPv6 unicast address family view:
peer { group-name | ipv6-address } allow-as-loop [ number ]
undo peer { group-name | ipv6-address } allow-as-loop
Default
The local AS number is not allowed to exist in the AS_PATH attribute of routes from a peer or peer group.
Views
BGP IPv4 unicast address family view, BGP-VPN IPv4 unicast address family view, BGP-VPNv4 address
family view, BGP IPv6 unicast address family view, BGP-VPN IPv6 unicast address family view, BGP
L2VPN address family view
Predefined user roles
network-admin
Parameters
group-name: Specifies a peer group by its name, a case-sensitive string of 1 to 47 characters. The peer
group must have been created.
ip-address: Specifies a peer by its IP address. The peer must have been created.
ipv6-address: Specifies a peer by its IPv6 address. The peer must have been created.
number: Specifies the number of times for which the local AS number can appear, in the range of 1 to
10. The default number is 1. If the number of times for which the local AS number appears in a route is
more than the specified number, BGP considers that a routing loop occurs and discards the route.
Usage guidelines
By default, BGP does not receive routes that contain the local AS number in the AS_PATH attribute to
avoid routing loops. However, in certain network environments (a Hub&Spoke network in MPLS L3VPN,
for example), 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.
Examples
# In BGP IPv4 unicast address family view, configure the number of times the local AS number can
appear in AS_PATH attribute of routes from peer group test as 2.
<Sysname> system-view
[Sysname] bgp 100
[Sysname-bgp] address-family ipv4 unicast
[Sysname-bgp-ipv4] peer test allow-as-loop 2
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