3Com S7902E, Руководство по настройке

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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/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/peer groups. In this way, these eBGP peers still think Router A is
in AS 2 and thus need not change their configurations. This feature ensures uninterrupted BGP
services.
Follow these steps to specify a fake AS number for a peer/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/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.
Configure AS number substitution
In MPLS L3VPN, if eBGP is used between PE and CE, sites in different geographical areas should have
different AS numbers assigned to ensure correct route advertisement. If different CEs use the same AS
number, you need to configure the corresponding PE to replace the AS number of the CE as its own AS
number. This feature is used for route advertisement only.
Figure 1-19 AS number substitution configuration
MPLS backbone
VPNv4_Update:10.1.0.0/16
RD:10.1.1.1/32
AS_PATH:800
EBGP_Update:10.1.1.1/32
AS_PATH:100,100
PE 1 PE 2
AS 800
EBGP_Update:10.1.1.1/32
AS_PATH:800
AS 800
AS 100
CE 1
CE 2