From: Gustavo Novais (gustavo.novais@novabase.pt)
Date: Thu Sep 22 2005 - 08:09:08 GMT-3
I think both work, but you complicate things more with the +)? because
you are saying that you allow the pattern [0-9], one or more times, in
order to take care of matching the neighbor AS 1, 12, 123, 1234, or
12345, but then you limit ALL the occurrence (_[0-9]+) to zero or one
times, because of the directly connected neighbor
I think personally that it is more elegant to do the first.
As both work it would be a matter of opinion and mood of the proctor...
If he wants the elegant solution, or if he only looks at the bgp table
and does not care on how you solved it...
You may also wanto to see this document:
http://www.cisco.com/warp/public/459/26.html#t5
which chooses the * option
________________________________
From: Schulz, Dave [mailto:DSchulz@dpsciences.com]
Sent: quinta-feira, 22 de Setembro de 2005 11:50
To: Gustavo Novais
Cc: ccielab@groupstudy.com
Subject: RE: BGP Reg Exp
A number of people gave this as the solution:
ip as-path access-list 1 permit ^123(_[0-9]+)?$
Asterisk vs. Question mark at that end? Which would be more correct as
the solution? I would assume the * would do it since it is zero or more
to match.
Dave
-----Original Message-----
From: Gustavo Novais
To: simon hart; Schulz, Dave; syv@911networks.com; Leigh Harrison
Cc: Cisco certification
Sent: 9/22/2005 5:31 AM
Subject: RE: BGP Reg Exp
Why not use ^123_[0-9]* instead of + and the extra line?
Since the * matches the chars 0 or more times, and the _ char is not
included within [0-9] that would match either ^123$ or ^123_456$ or
^123_65535$
If in doubt of your as-path list you can always do sh ip bgp regexp to
see what matches or not.
Gustavo
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
simon hart
Sent: quinta-feira, 22 de Setembro de 2005 7:45
To: Schulz, Dave; syv@911networks.com; Leigh Harrison
Cc: Cisco certification
Subject: RE: BGP Reg Exp
Dave,
this was the original answer that I gave:
The Reg Exp you are probably looking for is
^123(_[0-9]+)?$
Which transpires as
^ begins with 123
()? anything within the brackets can occur either no times or once
()?$ so now it will end with either 0 occurrence within the bracket or
one occurrence
[0-9)+ match 1 or more sequence of the numbers 0 to 9
Thus ^123(_[0-9]+)?$ will give you the directly attached AS and there
directly attached clients
A tip for when you doing the lab. The Doc CD has a section regular
expressions within the configuration guide, Part 1 Cisco IOS User Guide,
Using the Command-Line Interface
http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/
ffun
_c/ffcprt1/fcf001.htm#1002051
HTH Simon
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
Schulz, Dave
Sent: 22 September 2005 02:28
To: syv@911networks.com; Leigh Harrison
Cc: Cisco certification
Subject: RE: BGP Reg Exp
Leigh -
I didn't see a follow up on your question. But I believe that if you
want to have the AS123 and it's neighbors, you will need to two lines:
ip as-path access-list 1 permit ^123
ip as-path access-list 1 permit ^123_[0-9]+
Dave Schulz,
Email: dschulz@dpsciences.com
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
syv@911networks.com
Sent: Sunday, September 18, 2005 5:33 PM
To: Leigh Harrison
Cc: Cisco certification
Subject: Re: BGP Reg Exp
Leigh Harrison wrote:
> All,
>
> If I wanted to allow a neighboring AS(123) and his directly connected
> AS's to be seen as routes to me, could this be written as:
>
> ip as-path access-list 1 permit ^123_[0-9]*$
http://www.911networks.com/pages/cisco/bgp/regular-expressions.php
> OR
> ip as-path access-list 1 permit ^123_.*$ OR ip as-path access-list 1
> permit ^.+_[0-9]*$ OR ip as-path access-list 1 permit ^.+_.*$ OR ip
> as-path access-list 1 permit ^[0-9]+_[0-9]*$ OR ip as-path access-list
> 1 permit ^[0-9]+_.*$
>
> Could someone have a quick look and let me know if that would be the
> same thing ? I think I'm getting there!! The only niggle in the back
> of my mind is ^123_.*$ (for example), would I need a "+" after the 123
?
>
> Many thanks,
> LH
>
>
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