R0106-HP MSR Router Series Layer 3 - IP Routing Configuration Guide(V7)

255
Ste
p
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. 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 EBGP 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. If two CEs
connected to different PEs use the same AS number, you must configure AS number substitution on each
PE. This can replace the AS number in route updates originated by the remote CE as its own AS number
before advertising them to the connected CE.
Figure 62 AS number substitution configuration (in an IPv4 network)
For example, as shown in Figure 62, CE 1 and CE 2 use the same AS number 800. To ensure
bidirectional communication between the two sites, configure AS number substitution on PE 2. PE 2
replaces AS 800 with AS 100 for the BGP route update originated from CE 1 before advertising it to CE
2. Perform the same configuration on PE 1.
To configure AS number substitution for a peer or peer group (IPv4 unicast/multicast address family):
Ste
p
Command Remarks
1. Enter system view.
system-view
N/A