H3C Technologies H3C S10500 Series Switches - Manual (Page 233)

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To do… Use the command… Remarks
Enter system view system-view —
Enter BGP view bgp as-number —
Permit local AS number to appear in routes
from a peer or peer group and specify the
appearance times
peer { group-name | ip-address }
allow-as-loop [ number ]
Optional
By default, the local AS
number is not allowed.
Disable BGP from considering AS_PATH during best route selection
Follow these steps to disable BGP from considering AS_PATH during best route selection:
To do… Use the command… Remarks
Enter system view system-view —
Enter BGP view bgp as-number —
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.
Specify 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.
Follow these steps to specify a fake AS number for a peer or peer group:
To do… Use the command… Remarks
Enter system view system-view —
Enter BGP view bgp as-number —
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
NOTE:
This command is only applicable to an eBGP peer or peer group.
Configure 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 different CEs 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.