HPE FlexNetwork HSR6800 Configuration Manual page 229

Specifying a fake AS number for a peer or peer group
When Router A in AS 2 is moved to AS 3, you can configure Router A to specify a fake AS number of
2 for created connections to EBGP peers or peer groups. In this way, these EBGP peers still think
Router A is in AS 2 and need not change their configurations. This feature ensures uninterrupted
BGP services.
To specify a fake AS number for a peer or peer group:
Step
Enter system view.
1.
Enter BGP view or
2.
BGP-VPN instance view.
Specify a fake AS number
3.
for a peer or peer group.
Configuring AS number substitution
In MPLS L3VPN, if EBGP is used between PE and CE, sites in different geographical areas must
have different AS numbers assigned to ensure correct route advertisement. If CEs in different
geographical areas use the same AS number, you must configure the relevant PE to replace the AS
number of the CE as its own AS number. This feature is used for route advertisement only.
Figure 72 AS number substitution configuration
As shown in the above figure, CE 1 and CE 2 use the same AS number of 800. If AS number
substitution for CE 2 is configured on PE 2, and PE 2 receives a BGP update sent from CE 1, PE 2
replaces AS number 800 as its own AS number 100. Similar configuration must also be made on PE
1.
Use AS number substitution only in the specific scenario. Improper configuration can result in routing
loops.
To configure AS number substitution for a peer or peer group:
Step
Enter system view.
1.
Command
system-view
•
Enter BGP view:
bgp as-number
•
Enter BGP-VPN instance view:
a. bgp as-number
b. ipv4-family vpn-instance
vpn-instance-name
peer { group-name | ip-address }
fake-as as-number
Command
system-view
217
Remarks
N/A
Use either method.
Optional.
Not specified by default.
This command is only
applicable to an EBGP peer or
peer group.
Remarks
N/A