From: ying chang (ying_c@xxxxxxxxxxx)
Date: Thu Apr 04 2002 - 02:02:20 GMT-3
Hi Manny,
Sorry about the confusion, I'm not saying anything new. What I'm trying to
say is when we are talking about "_300_", don't forget AS300 can be
anywhere in the path. So we don't need to write statements like:
ip as-path access-list 1 permit ^300$
ip as-path access-list 1 permit _300$
ip as-path access-list 1 permit ^300_
ip as-path access-list 1 permit _300_
A single statemnet
ip as-path access-list 1 permit _300_
would cover all.
Please correct me if I'm wrong.
Thanks,
Chang
>From: Manny Gonzalez <manny@nyp.org>
>To: ying chang <ying_c@hotmail.com>
>CC: gonzalu@nyp.org, mamoor@ieee.org, ccielab@groupstudy.com
>Subject: Re: BGP AS-PATH
>Date: Wed, 03 Apr 2002 22:09:29 -0500
>
>Ying Chang,
>
>I am sorry but I did not understand your response. Can you re-write your
>post with a more descriptive explanation of what you mean? You claim
>that "_" will match specific AS-PATH regular expressions?? I don't get
>your intended meaning.
>
>I know that the underscore matches a lot of things, including beginning
>and end of string. So what are you trying to say exactly?
>
>TIA
>
>Manny Gonzalez.....................CCIE# 9013
>CORE Resources.......NY Presbyterian Hospital
>
>ying chang wrote:
> >
> > "_" is a tricky one, it matches ^, $, (, ), {, }, " ", ",", or "_". That
> > means it will covers ^300$, ^300_, _300$ and _300_.
> >
> > Chang
> >
> > >From: "Manny Gonzalez" <gonzalu@nyp.org>
> > >Reply-To: "Manny Gonzalez" <gonzalu@nyp.org>
> > >To: Ahmed Mamoor Amimi <mamoor@ieee.org>
> > >CC: ccielab@groupstudy.com
> > >Subject: Re: BGP AS-PATH
> > >Date: Wed, 03 Apr 2002 18:15:15 -0500
> > >
> > >Well, all look okay except:
> > >
> > > > ^300$ = orignating from 300
> > >
> > >I believe this actually means from the CONNECTED AS 300, not ORIGINATED
> > >from there... for ORIGINATED in AS300 I believe you would do
> > >
> > >_300$
> > >
> > >The other one is
> > >
> > > > ^300 200$ = routes from AS 300 and 200 or 200 and 300
> > >
> > >I believe you also have this one incorrectly interpreted. I believe it
> > >actually means that the PATH MUST BE 300 200 in exactly that order. For
> > >200 300 you would need ^200 300$. I believe it is a literal expresion.
> > >
> > >If I am wrong I will be corrected soon enough.
> > >
> > >Also, I would be careful with your interpretation of forward or
> > >backwards paths... Let's say we stay on the same ballpark and use
>common
> > >terminology. I prefer the term ORIGINATE and TRANSIT and CONNECTED as
> > >descriptive terms in an as-path. We all agree that the origin is at the
> > >righ hand side of the string and the connected AS is always on the left
> > >hand side of the string... etc. etc. :-))
> > >
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