From: Bauer, Rick (BAUERR@xxxxxxxxxxx)
Date: Thu Aug 22 2002 - 16:23:20 GMT-3
I'm giving a "sho ip bgp reg" not an as-path filter.
-----Original Message-----
From: Edward Monk [mailto:emonk@att.net]
Sent: Thursday, August 22, 2002 3:18 PM
To: 'Bauer, Rick'
Cc: ccielab@groupstudy.com
Subject: RE: regexp fun (was RE: Filtering BGP updates using ip as-path
ac cess-lists)
Still not correct. Besides being reverse logic what I mean by that is
your regexp says match routes originated in AS 1000 not 10 as Brian's
criteria called for. But accounting for that it still would not work.
The beginning would match 1 10 100 1000 10000 at the very least.
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Bauer, Rick
Sent: Thursday, August 22, 2002 12:21 PM
To: 'Brian McGahan'; 'elping'; 'Michael Snyder'
Cc: 'ccielab@groupstudy.com'
Subject: RE: regexp fun (was RE: Filtering BGP updates using ip as-path
ac cess-lists)
Not correct I need another "?"
sh ip bgp reg ^10 ?.* 100 ?.* 1000$
Rick, #9482
-----Original Message-----
From: Bauer, Rick
Sent: Thursday, August 22, 2002 2:09 PM
To: 'Brian McGahan'; 'elping'; 'Michael Snyder'
Cc: ccielab@groupstudy.com
Subject: RE: regexp fun (was RE: Filtering BGP updates using ip as-path
access-lists)
Okay Brain, you intrigued me. Here is the regular expression for your
question. You helped me find a new use for the "?". Cool stuff!
sh ip bgp reg ^10 ?.* 100 .* 1000$
Rick, #9482
-----Original Message-----
From: Brian McGahan [mailto:brian@cyscoexpert.com]
Sent: Wednesday, August 21, 2002 10:21 AM
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 - 19:48:34 GMT-3