236
Step Command
Remarks
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.
Advertise a fake AS number to
a peer or peer group.
peer
{
group-name
|
ipv6-address
}
fake-as
as-number
By default, no fake AS number is
advertised to a peer or peer group.
This command applies to only
EBGP peers or EBGP peer groups.
Configuring AS number substitution
IMPORTANT:
Do not configure AS number substitution in normal circumstances. Otherwise, routing loops might occur.
To use BGP between PE and CE in MPLS L3VPN, VPN sites in different geographical areas should have
different AS numbers. Otherwise, BGP discards route updates containing the local AS number.
Figure 59
AS number substitution configuration (in an IPv4 network)
For example, as shown in
Figure 59
, CE 1 and CE 2 use the same AS number 800. To implement
bidirectional communication between the two sites, configure AS number substitution on PE 2 to replace
AS 800 as AS 100 for the BGP route update originated from CE 1 before advertising it to CE 2, and
perform the same configuration on PE 1.
To configure AS number substitution for a peer or peer group (IPv4 unicast/multicast address family):
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.
Configure AS number
substitution for a peer or peer
group.
peer
{
group-name
|
ip-address
}
substitute-as
By default, AS number substitution
is not configured.
