From: elping (elpingu@xxxxxxxxxx)
Date: Sun Aug 18 2002 - 15:44:47 GMT-3
I agree with you bryan with the
^4_[0-9]*$
i was showing the results of the discussed expressions and thei results..
but clarify
what was it that i missed with the 0..i though i put it in
Brian McGahan 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]*$. If they are the same, why not use the shorter one?
> >
> > Please Advise
> >
> > -----Original Message-----
> > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
> Of
> > Chaim Gev
> > Sent: Thursday, August 15, 2002 8:13 AM
> > To: msnyder@ldd.net; raj.bahad@totalise.co.uk
> > Cc: ccielab@groupstudy.com
> > Subject: RE: Filtering BGP updates using ip as-path access-lists
> >
> > The "*" means "match 0 or more sequences of the pattern" which is null
> > in
> > your suggestion.
> > ^_4_[0-9]*$ 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 - 19:48:29 GMT-3