SROS Command Line Interface Reference Guide
BGP Neighbor Configuration Command Set
5991-2114
© Copyright 2006 Hewlett-Packard Development Company, L.P.
1318
local-as
<as-number>
Use the
local-as
command to specify an autonomous system (AS) number for the unit to use when commu-
nicating with this BGP neighbor. Use the
no
form of this command to return to default settings.
Syntax Description
<as-number>
Specifies the AS number to use when communicating with this neighbor. Must be
different than the AS number for this router and the peer router. Only valid for
eBGP connections. Range is 0 to 65,535.
Default Values
By default, no local AS number is defined. The router’s BGP AS number is used.
Functional Notes
This command substitutes a different AS number to be used for communicating with this BGP neighbor.
(other than the one the router is actually a member of). This can be used to satisfy network designs
requiring a customer to appear as one AS number when communicating with one Internet service provider
(ISP) and another when communicating with another ISP.
Usage Examples
The following example configures this BGP neighbor’s AS number to be
300
:
ProCurve(config)#
router bgp 65000
ProCurve(config-bgp)#
neighbor 172.24.3.192
ProCurve(config-bgp-neighbor)#
local-as 300
Technology Review
This router appears (to the peer router) to be in the AS specified with the
local-as
command. In network
advertisements from routers using the
local-as
command, the first router’s true AS number (the number
specified using the
router bgp as-number
command) is prepended to the AS path attribute, then the local
AS (the number specified using the
local-as
command) is prepended to the AS path attribute. This makes
it appear that the path from this router to the network is first through the local AS, and then through the true
AS. To further illustrate, consider the following example network.
In this network:
•
Router A is in AS 100.
•
Router B is in AS 300.
•
Router A is an eBGP peer with Router B.
•
Router A’s connection to Router B specifies a
local-as
of 200.
•
Router B is configured to connect to Router A in AS 200.
Therefore:
•
To Router B, all aspects of Router A appear as AS 200.
•
Networks advertised from Router A to Router B will have the AS path
200 100
prepended to the AS path
attribute.
•
Router A will add AS 200 to the AS path of networks learned from Router B.
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