From: rick@iptool.net
Date: Sat Jan 10 2004 - 19:17:17 GMT-3
I never really understood regular expresions very good. I do not use them at
all in my job and this makes it more dificult to remember them. Has anybody
found a method for memorizing them or at least a comprehensive guide on
them? I practise them over and over in a lab environment until I think I
have them down then come back a week later and can't remember any of them.
Thanks
----- Original Message -----
From: "Scott Morris" <swm@emanon.com>
To: "'Nathasha Aleyevka'" <naleyevka@yahoo.com>; <ccielab@groupstudy.com>
Sent: Saturday, January 10, 2004 4:05 PM
Subject: RE: Regular Expressions
> Your first one there matches all prefixes ORIGINATING in AS 900 (that will
> be the end of the string, or the oldest AS).
>
> Your third one, I'm not entirely sure what it accomplishes other than
going
> through SOMETHING! :)
>
> Your last one, you have to remember that the _ character represents a
comma,
> {, }, (, ), beginning, end or space within a string. For AS paths, we
> primarily think of this as the space between AS numbers in the path. So
you
> are mathing something transiting 99 and 0 or 1 other AS, but originating
> from 75. Not the last two digits of 75, but 75 itself.
>
> If you had the last string as ...75 (since 5 characters is the max set
> anyway), then that would be great for anything ending in 75. But the
> "(_|_.*_)" refers to the single space or anything within that one AS set
> (between spaces). If you wanted to have it pass through multiple (as many
> as necessary) systems, you woul duse the "(_|_.*_)*" instead. That * on
the
> outside of the parentheses treats the entire thing as a "0 or more of"
> match.
>
> Regurlar expressions are enough to make your brain hurt. :)
>
>
> Scott Morris, CCIE4 (R&S/ISP-Dial/Security/Service Provider) #4713, CISSP,
> JNCIS, et al.
> IPExpert CCIE Program Manager
> IPExpert Sr. Technical Instructor
> swm@emanon.com/smorris@ipexpert.net
> http://www.ipexpert.net
>
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> Nathasha Aleyevka
> Sent: Saturday, January 10, 2004 4:46 PM
> To: ccielab@groupstudy.com
> Subject: Regular Expressions
>
> Hi,
> I have created the following 4 REs:
> Would you please go over'em and advise me:
>
> 1) _900$ matches all the prefixes learned from BB1(900)
>
> 2) _500_ matches all the prefixes which transited AS500 :
>
> 3) _|.* any neighbor or AS using my terms
>
> 4) _99(_|_.*_)75$ matches any path that goes through AS99 and ends
> with an AS# whos the last 2 digits are 75
>
> I used the infot from
>
http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/fdia
> l_c/fnsprt13/dafaapre.htm
>
> Thank you very much
> Nathasha
>
>
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