From: Brian McGahan (bmcgahan@internetworkexpert.com)
Date: Sun Feb 01 2004 - 17:59:28 GMT-3
I'm not sure how you would keep some routers inside your AS
confederated and some not... instead what you need is an expression that
will match locally originated routes as well as those from your
confederation peers. This will do the trick:
^(\(.*\))?$
HTH,
Brian McGahan, CCIE #8593
bmcgahan@internetworkexpert.com
Internetwork Expert, Inc.
http://www.InternetworkExpert.com
Toll Free: 877-224-8987
Direct: 708-362-1418 (Outside the US and Canada)
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> Bob Sinclair
> Sent: Saturday, January 31, 2004 5:16 PM
> To: Hossam; ccielab@groupstudy.com
> Subject: Re: AS-Path Filtering with BGP Confiderations!
>
> Sam,
>
> I can confirm that your AS 200 will not show up within the sub-ASs. So if
> you do sho ip b reg ^$ you will see routes from the local sub-as, not
> routes
> from AS 200.
>
> To do an as-path filter that will send only routes from within AS 200, you
> would have to include the empty path, ^$, as well as all other sub-ASs.
>
> This is quite inconvenient! For just this reason, perhaps it would be
> desirable in a real-world implementation to keep your AS border routers
> out
> of your confederations. That way you can easily permit ^$ to allow only
> your own routes outbound.
>
> HTH,
>
> Bob Sinclair
> CCIE #10427, CISSP, MCSE
> www.netmasterclass.net
>
> ----- Original Message -----
> From: "Hossam" <sam6626@yahoo.com>
> To: <ccielab@groupstudy.com>
> Sent: Saturday, January 31, 2004 5:41 AM
> Subject: AS-Path Filtering with BGP Confiderations!
>
>
> > I am trying to configure a BGP router R2 in (AS 65 256 and Bgp
> Confideration indentifier 200) to limit it advertesment to its EBGP
> neighbour (R4 in AS 300) to the routes that was originated in AS 200.
> >
> > I noticed that while i am AS-path filtering (either via filter-list or a
> route map) and an ip as-path accesslist that permits only ^200$, nothing
> gets advertised to the neighbour R4.
> >
> > Once i remove the as-path filtering i get the routes with AS-path = 200
> at
> R4 as expected.
> >
> > I think the problem is that R2 has the routes with AS-path = (65078)
> cause
> of the confidertaions in its BGP table.
> > It seems that the IOS does the filtering first and then it strips of the
> confiderations as-path just before advertesting the routes to EBGP
> neighbour.
> >
> > Now the question is: what is the best way to do the filtering in this
> case? i hate the idea of filtering on the SUB ASs...any ideas...
> >
> > Thanks..
> > SAM
> >
> >
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