From: Tim O'Brien (tobrien@xxxxxxxxxxxx)
Date: Thu Mar 28 2002 - 21:48:25 GMT-3
You can test it at ner-routes.bbnplanet.net
Tim
9015
-----Original Message-----
From: Bob Sinclair [mailto:bsin@erols.com]
Sent: Thursday, March 28, 2002 7:43 PM
To: Tim O'Brien
Cc: ccielab@groupstudy.com
Subject: Re: AS-path access-list
Tim,
Based on my reading or Halabi, the two statements seem equivalent:
ip as-path access-list 4 permit ^200_[0-9]*$
and
ip as-path access-list 4 permit ^200 ?[0-9]*$
The underscore can mean most anything, including end of string. So it would
match ^200$ to identify routes from the immediate neighbor.
The underscore can also be a space, then [0-9]*$ should match any number
(including zero) of consecutive numerals. Looks to me like both would work.
The first example may be easier to remember, but I would want to test it
before betting $1,250 on it! I know Halabi's works.
-Bob
----- Original Message -----
From: "Tim O'Brien" <tobrien@cinci.rr.com>
To: "Bob Sinclair" <bsin@erols.com>; "Hongtu Wang" <hwang1073@rogers.com>
Cc: <ccielab@groupstudy.com>
Sent: Thursday, March 28, 2002 7:29 PM
Subject: RE: AS-path access-list
> I found this one on the Cisco site. What do you think?
>
> ip as-path access-list 4 permit ^200_[0-9]*$
>
> http://www.cisco.com/warp/public/459/41.shtml#2
>
> Tim
> 9015
>
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
> Bob Sinclair
> Sent: Thursday, March 28, 2002 6:37 PM
> To: Hongtu Wang
> Cc: ccielab@groupstudy.com
> Subject: Re: AS-path access-list
>
>
> Hongtu,
>
> I believe you will find that the following expression will work with the
> fewest number of statements to define "routes from AS 200 and its
> neighbors":
>
> ip as-path access-list 4 permit ^200 ?[0-9]*$
>
> It is discussed in detail in Halabi's book "Internet Routing
Architectures",
> on page 376. The meaning of regular expression characters is explained on
> page 187.
>
> -Bob
>
>
>
> ----- Original Message -----
> From: "Hongtu Wang" <hwang1073@rogers.com>
> To: <ccielab@groupstudy.com>
> Sent: Monday, March 25, 2002 10:29 PM
> Subject: AS-path access-list
>
>
> > Hi,
> >
> > My topology is:
> >
> > R1(AS100)----R2(AS200)----AS50---AS250
> >
> > If I only want to accept routes come from AS200 and all AS directly
> connect to AS200 (AS50 in my topology), how to write as-path access-list
on
> R1?
> >
> > Thanks
> >
> > Hongtu Wang
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