From: Hoyle, Anthony (AL) (ALHoyle@dow.com)
Date: Thu Nov 20 2003 - 13:46:01 GMT-3
Remember the regular expression for routes that originate will be _2$ (I only use that one if the AS is a couple of hops away.
If it is an AS that is directly connected I tend to use ^2$.
Anthony H
EDS
WAN Infrastructure Analyst
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of Kelly, Russell G
Sent: Thursday, November 20, 2003 11:07 AM
To: ccielab@groupstudy.com
Subject: FW: BGP Regular Expressions for as-path filtering
Or possibly
ip as-path access-list 1 permit _2_
> -----Original Message-----
> From: Kelly, Russell G
> Sent: 20 November 2003 15:58
> To: ccielab@groupstudy.com
> Subject: BGP Regular Expressions for as-path filtering
>
> I have 3 AS's chained together as below:
>
> | AS 1 | -> | AS2 | -> | AS3 |
>
> AS1 and AS2 have all routers running BGP but AS redistributes BGP into
> OSPF (and redistributes it's own OSPF routes into BGP). I want AS3
> to only redistribute routes originating in AS1 and AS2 into OSPF (and
> not redistribute these back into BGP!!!!!) and I am trying to come up
> with a regular expression to achieve this. I am not too sure on the
> as-path 1 ^2 1$ regular expression, or the redistribution tagging for
> AS1. Will the 'better' reg expression be:
>
> ip as-path access-list 1 permit ^2.* (i.e. anything coming through
> AS2???)
>
> The route maps and as-path statements currently are:
>
> ip as-path access-list 1 permit ^2 1$
> ip as-path access-list 2 permit ^2$
>
> route-map BGP2OSPF permit 10
> description Allow AS1 Routes
> match as-path 1
> set metric 100
> set metric-type type-1
> set tag 2 1
> !
> route-map BGP2OSPF permit 20
> description Allow AS2 Routes
> match as-path 2
> set metric 100
> set metric-type type-1
> set tag 2
> !
>
> route-map OSPF-TO-BGP deny 10
> match tag 2
> !
> route-map OSPF-TO-BGP deny 20
> match tag 2 1
> !
> route-map OSPF-TO-BGP permit 30
>
> Russ
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