H3C Technologies H3C S5560 Series Switches - Manual (Page 252)

236
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):
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 IPv6 unicast
address family view or
BGP-VPN IPv6 unicast
address family view.
address-family ipv6 [ 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 | ipv6-address
[ prefix-length ] } allow-as-loop
[ number ]
By default, the local AS number is
not allowed in routes from a peer
or peer group.