R3102-R3103-HP 6600/HSR6600 Routers Layer 3 - IP Routing Configuration Guide

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Disabling BGP from considering AS_PATH during best route selection
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. ipv4-family vpn-instance
vpn-instance-name
Use either method.
3. Disable BGP from considering
AS_PATH during best route
selection.
bestroute as-path-neglect
Optional.
By default, BGP considers
AS_PATH during best route
selection.
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 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. ipv4-family vpn-instance
vpn-instance-name
Use either method.
3. Specify a fake AS number for
a peer or peer group.
peer { group-name | ip-address }
fake-as as-number
Optional.
Not specified by default.
This command is only
applicable to an EBGP 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.