Command:

ip as-path access-list


Mode:

Router(config)#

Syntax:

 

ip as-path access-list access-list-number {permit | deny } as-regular-expression

no ip as-path access-list access-list-number {permit | deny } as-regular-expression


Syntax Description:

 

access-list-number

Integer from 1 to 199 that indicates the regular expression access list number.

permit

Permits access for matching conditions.

deny

Denies access to matching conditions.

as-regular-expression

Autonomous system in the access list using a regular expression. See the "Regular Expressions" appendix in the Dial Solutions Command Reference for information about forming regular expressions.


Command Description:

 

To define a BGP-related access list, use the ip as-path access-list global configuration command. To disable use of the access list, use the no form of this command.

Usage Guidelines: 

An access list filter can be spcified on both inbound and outbound BGP routes. In addition, weights can be assigned based on a set of filters. Each filter is an access list based on regular expressions. If the regular expression matches the representation of the autonomous system path of the route as an ASCII string, then the permit or deny condition applies. The autonomous system path does not contain the local autonomous system number. Use the ip as-path access-list global configuration command to define an BGP access list, and the neighbor router configuration command to apply a specific access list.


Example:

 

The following example specifies that the BGP neighbor with IP address 128.125.1.1 is not sent advertisements about any path through or from the adjacent autonomous system 123:

Router (config)#ip as-path access-list 1 deny _123_
Router (config)#ip as-path access-list 1 deny ^123$

Router (config)#router bgp 109
Router (config-router)#network 131.108.0.0
Router (config-router)#neighbor 129.140.6.6 remote-as 123
Router (config-router)#neighbor 128.125.1.1 remote-as 47
Router (config-router)#neighbor 128.125.1.1 filter-list 1 out


Misconceptions:

 

None


Related Commands:

 

neighbor filter-list

 

 

 


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