From: Brian McGahan (brian@xxxxxxxxxxxxxxx)
Date: Mon Aug 19 2002 - 14:32:24 GMT-3
^4_[0-9]*$
This is matching prefixes originated in AS 4, and prefixes originated in
the AS's directly connected to AS 4. If you want to show everything that
is learned from AS 4, you could take the $ off of the end:
^4_[0-9]*
But that's the same as just saying:
^4_
I didn't read this whole thread, but I'm assuming the discussion was
about prefixes originated in AS 4 and AS 4's customer's routes.
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: Song Mu [mailto:songmu@yahoo.com]
Sent: Monday, August 19, 2002 12:17 PM
To: Brian McGahan; 'elping'; 'Michael Snyder'
Cc: steven.j.nelson@bt.com; ccielab@groupstudy.com
Subject: RE: Filtering BGP updates using ip as-path access-lists
With the $ can only show one AS# after AS#4. It will show all the
prepend AS#s if the $ been removed from the end.
Song
--- Brian McGahan <brian@cyscoexpert.com> wrote:
> Elping, don't forget to match the 0.
>
> If you're trying to match routes learned from AS 4, and their
> customer routes, the string would be:
>
> ^4_[0-9]*$
>
> Translating to:
>
> ^4_ Learned from AS 4
> [0-9]* 0 or more instances of any character 0 through 9
> $ end of string
>
> As Elping said, the easiest way to practice these regular
> expressions is to test them on a route-server.
>
> telnet://route-server.exodus.net
>
> 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
> >
>
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