From: Abidin Kahraman (kahramana@xxxxxxxxxxxxxxx)
Date: Wed Aug 21 2002 - 12:01:39 GMT-3
Is this ok ?
^1000_100(_.+_)10$
I`ve tried on my router and it seems ok, what is your ideas?
Abidin.
-----Original Message-----
From: Brian McGahan [mailto:brian@cyscoexpert.com]
Sent: Wednesday, August 21, 2002 5:21 PM
To: 'Brian McGahan'; 'elping'; 'Michael Snyder'
Cc: steven.j.nelson@bt.com; ccielab@groupstudy.com
Subject: regexp fun (was RE: Filtering BGP updates using ip as-path
access-lists)
Did we give up already?
<snip>
Try this one: All routes originated in AS 10, passed through AS
100, and learned from AS 1000. (In one line)
HTH
Brian McGahan, CCIE #8593
Director of Design and Implementation
brian@cyscoexpert.com
CyscoExpert Corporation
Internetwork Consulting & Training
http://www.cyscoexpert.com
Voice: 847.674.3392
Fax: 847.674.2625
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
elping
Sent: Sunday, August 18, 2002 9:46 AM
To: Michael Snyder
Cc: steven.j.nelson@bt.com; ccielab@groupstudy.com
Subject: Re: Filtering BGP updates using ip as-path access-lists
steve :
consider that
^4 [0-9]* will be an exact 4 and some other number
so any routes coming from 4 will not show up...
i put your theory to the test on an actual Bgp routing table observ.
I am using 7788 and all it's connected routes..
in summary the underscore will allow 7788 routes and it's
connected...without the underscore
you are saying a exact 7788 and it's connected.....see for yourself...
if i mistyped or got you thoughts wrong feel free to correct..
using your string i obtain nothing
route-server.east>sh ip bgp reg ^7788 [0-9]* [0-9]*$
route-server.east>
observ the string sh ip bgp reg ^7788_[1-9]*$ ---that is with the
underscore
route-server.east>sh ip bgp reg ^7788 [0-9]* [0-9]*$
route-server.east>sh ip bgp reg ^7788_[1-9]*$
BGP table version is 97446699, local router ID is 216.191.65.118
Status codes: s suppressed, d damped, h history, * valid, > best, i -
internal
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*>i64.26.128.0/18 216.191.224.1 100 0 7788 7788 i
* i 216.191.224.1 100 0 7788 7788 i
*>i192.203.106.0 216.191.224.1 100 0 7788 i
* i 216.191.224.1 100 0 7788 i
*>i192.222.1.0 216.191.224.1 100 0 7788 i
* i 216.191.224.1 100 0 7788 i
*>i192.222.2.0/23 216.191.224.1 100 0 7788 i
* i 216.191.224.1 100 0 7788 i
*>i192.222.4.0/22 216.191.224.1 100 0 7788 i
* i 216.191.224.1 100 0 7788 i
*>i192.222.8.0 216.191.224.1 100 0 7788 i
* i 216.191.224.1 100 0 7788 i
*>i198.96.127.0 216.191.224.1 100 0 7788 i
* i 216.191.224.1 100 0 7788 i
*>i198.96.199.0 216.191.224.1 100 0 7788 i
* i 216.191.224.1 100 0 7788 i
*>i199.71.68.0 216.191.224.1 100 0 7788 i
* i 216.191.224.1 100 0 7788 i
*>i204.138.103.0 216.191.224.1 100 0 7788 i
* i 216.191.224.1 100 0 7788 i
*>i204.187.103.0 216.191.224.1 100 0 7788 i
* i 216.191.224.1 100 0 7788 i
*>i204.225.145.0 216.191.224.1 100 0 7788 i
* i 216.191.224.1 100 0 7788 i
*>i205.207.175.0 216.191.224.1 100 0 7788 i
* i 216.191.224.1 100 0 7788 i
*>i205.233.68.0 216.191.224.1 100 0 7788 i
* i 216.191.224.1 100 0 7788 i
*>i206.51.251.0 216.191.224.1 100 0 7788 i
* i 216.191.224.1 100 0 7788 i
*>i206.191.0.0/18 216.191.224.1 100 0 7788 7788 i
* i 216.191.224.1 100 0 7788 7788 i
*>i209.217.64.0/18 216.191.224.1 100 0 7788 7788 i
* i 216.191.224.1 100 0 7788 7788 i
route-server.east>
observe without the underscore sh ip bgp reg ^7788 [1-9]*$
route-server.east>sh ip bgp reg ^7788 [1-9]*$
BGP table version is 97446794, local router ID is 216.191.65.118
Status codes: s suppressed, d damped, h history, * valid, > best, i -
internal
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*>i64.26.128.0/18 216.191.224.1 100 0 7788 7788 i
* i 216.191.224.1 100 0 7788 7788 i
*>i206.191.0.0/18 216.191.224.1 100 0 7788 7788 i
* i 216.191.224.1 100 0 7788 7788 i
*>i209.217.64.0/18 216.191.224.1 100 0 7788 7788 i
* i 216.191.224.1 100 0 7788 7788 i
route-server.east>sh ip bgp reg ^7788_[1-9]*$
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 - 19:48:31 GMT-3