From: Omer Ansari (omer@xxxxxxxxxx)
Date: Sun Aug 18 2002 - 14:07:54 GMT-3
Mike,
the spaces in your regexp automatically nullify any routes originating
from AS4 right?
a little digression: anyone care to explain the difference between a comma
(,) and a space ( ) in a regexp?
are commas there for confederations?
On Thu, 15 Aug 2002, Michael Snyder wrote:
> _ (Matches a comma (,), left brace ({), right brace (}), the beginning
> of the input string, the end of the input string, or a space.
>
> Steve I just wanted to match a space. Thats why I didn't use _ , Cisco
> shows examples of not using _ to match spaces. In other words, a space
> char will match a space character.
>
> I stand by my expression of ^4 [0-9]* [0-9]*$
>
>
> I think another legal expression would be ^4 12 16 3$ notice that _
> isn't needed.
>
> -----Original Message-----
> From: steven.j.nelson@bt.com [mailto:steven.j.nelson@bt.com]
> Sent: Thursday, August 15, 2002 10:14 AM
> To: msnyder@ldd.net
> Subject: RE: Filtering BGP updates using ip as-path access-lists
>
> Michael
>
> You have missed out the _
>
>
> ^4_[0-9]*_[0-9]*$
>
> Steve
>
> -----Original Message-----
> From: Michael Snyder [mailto:msnyder@ldd.net]
> Sent: 15 August 2002 15:53
> To: 'Chaim Gev'
> Cc: ccielab
> Subject: RE: Filtering BGP updates using ip as-path access-lists
>
>
> ^4 [0-9]* [0-9]*$
>
> Would match any AS that was directly connected to an AS that was
> directly connected to AS 4. Is this correct?
>
> Also I think the expression you cited ^_4_[0-9]*$ is different than
> ^4_[0-9]*$. If they are the same, why not use the shorter one?
>
> Please Advise
>
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> Chaim Gev
> Sent: Thursday, August 15, 2002 8:13 AM
> To: msnyder@ldd.net; raj.bahad@totalise.co.uk
> Cc: ccielab@groupstudy.com
> Subject: RE: Filtering BGP updates using ip as-path access-lists
>
> The "*" means "match 0 or more sequences of the pattern" which is null
> in
> your suggestion.
> ^_4_[0-9]*$ is more accurate if you are asked to filter exactly AS4 (and
> not
> AS14).
>
>
>
>
> >From: "Michael Snyder" <msnyder@ldd.net>
> >Reply-To: "Michael Snyder" <msnyder@ldd.net>
> >To: "'Raj'" <raj.bahad@totalise.co.uk>
> >CC: <ccielab@groupstudy.com>
> >Subject: RE: Filtering BGP updates using ip as-path access-lists
> >Date: Thu, 15 Aug 2002 07:52:31 -0500
> >
> >I'm no expert on as-path access-lists.
> >
> >But, I believe the $ is the main difference.
> >
> >^4_ anything beginning with as path 4.
> >
> >^4_[0-9]*$ anything beginning with as path 4 and ENDS with one
> >additional AS.
> >
> >Which brings up a question of mine,
> >
> >Why wouldn't ^4_*$ do the same thing?
> >
> >
> >
> >-----Original Message-----
> >From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> >Raj
> >Sent: Thursday, August 15, 2002 7:02 AM
> >To: ccielab@groupstudy.com
> >Subject: Filtering BGP updates using ip as-path access-lists
> >
> >Hi all,
> >
> >I've come across a scenario for which I require some clarification.
> >
> >I want to permit only networks originated from AS4, and AS's directly
> >attached to AS4. I use the following config to meet the requirements,
> >however I have come across documentation that has achieved the same
> >results
> >using a slightly different version. I've listed both of them below:
> >
> >ip as-path access-list 1 permit ^4_
> >
> >and the other being:
> >
> >ip as-path access-list 1 permit ^4_[0-9]*$
> >
> >Could someone please help clarify why one method would be preferred
> over
> >the
> >other?
> >
> >Thanks,
> >
> >Raj.
This archive was generated by hypermail 2.1.4 : Sat Sep 07 2002 - 19:48:28 GMT-3