Cisco Cisco IOS Software Release 12.2(27)SBC
BGP Support for Dual AS Configuration for Network AS Migrations
How to Configure Autonomous System Migration
4
Cisco IOS Release: Multiple releases (see the Feature History table)
3.
router bgp as-number
4.
neighbor ip-address remote-as as-number
5.
neighbor ip-address local-as [as-number [no-prepend [replace-as [dual-as]]]
6.
neighbor ip-address remove-private-as
7.
end
DETAILED STEPS
Command or Action
Purpose
Step 1
enable
Example:
Router> enable
Enables privileged EXEC mode.
•
Enter your password if prompted.
Step 2
configure
terminal
Example:
Router# configure terminal
Enters global configuration mode.
Step 3
router bgp
as-number
Example:
Router(config)# router bgp 100
Enters router configuration mode, and creates a BGP
routing process.
routing process.
Step 4
neighbor
ip-address remote-as as-number
Example:
Router(config-router)# neighbor 10.0.0.1
remote-as 200
Establishes a peering session with a BGP neighbor.
Step 5
neighbor
ip-address local-as [as-number
[no-prepend [replace-as [dual-as]]]]
Example:
Router(config-router)# neighbor 10.0.0.1
local-as 300 no-prepend replace-as dual-as
Customizes the AS_PATH attribute for routes received from
an eBGP neighbor.
an eBGP neighbor.
•
The replace-as keyword is used to prepend only the
local autonomous-system number (as configured with
the ip-address argument) to the AS_PATH attribute.
The autonomous-system number from the local BGP
routing process is not prepended.
local autonomous-system number (as configured with
the ip-address argument) to the AS_PATH attribute.
The autonomous-system number from the local BGP
routing process is not prepended.
•
The dual-as keyword is used to configure the eBGP
neighbor to establish a peering session using the real
autonomous-system number (from the local BGP
routing process) or by using the autonomous-system
number configured with the ip-address argument
(local-as).
neighbor to establish a peering session using the real
autonomous-system number (from the local BGP
routing process) or by using the autonomous-system
number configured with the ip-address argument
(local-as).
•
The example configures the peering session with the
10.0.0.1 neighbor to accept the real autonomous system
number and the local-as number.
10.0.0.1 neighbor to accept the real autonomous system
number and the local-as number.