From: Geert Nijs (geert.nijs@simac.be)
Date: Fri Jan 05 2007 - 17:11:00 ART
All,
The expression
_174(_[0-9]+)*\1*$
is not right. I expect problems with it.
The problem is the * after (_[0-9]+)*
This matches a number of times a number, so in the case of
174 174 174 174
the part between () could match ( 174 174)
In this case it is uncertain where the brackets should stop and where the \1 can start.....
Why not use the much simplier:
_174(_[0-9]+)*$
It matches _174 and any repeating of another number.....
The * means 0 or 1 times THAT BETWEEN brackets. So the number between () must be the same to match ???
If that is not the case - i am not sure how Cisco parses the RegEx -
than the following should also work:
_174(_[0-9]+)?(\1)*$
regards,
Geert
CCIE 13729
-----Oorspronkelijk bericht-----
Van: nobody@groupstudy.com [mailto:nobody@groupstudy.com] Namens Bit Gossip
Verzonden: donderdag 28 december 2006 23:47
Aan: Huizinga, Rene
CC: ccielab@groupstudy.com
Onderwerp: RE: BGP Reg Exp
Hi Rene, GS,
it seems to work quite erratically:
re1>show ip bgp regexp _174(_[0-9]+)*\1*$
.....
*>i24.73.165.0/24 213.46.161.250 0 250 0 174 33363 i
*>i24.73.234.0/24 213.46.161.250 0 250 0 174 33363
33363 i
*>i24.75.137.0/24 213.46.161.250 0 250 0 174 174 174
174 16810 30299 30299 30299 30299 30299 30299 30299 i
*>i24.75.140.0/24 213.46.161.250 0 250 0 174 174 174
174 16810 32425 i
....
Look at the last one !!
Luca.
On Wed, 2006-12-27 at 22:45 +0100, Huizinga, Rene wrote:
> Darn, not going well here today, forgetting the '*' after the first
> expression to match the 0 or more occurances...sorry about
> that...thinking of one thing, typing the other, that's what you get
> when being half-focussed/having other things on your mind as well...
> Probably one of the reasons why some people are failing a lab... :(
>
> So ^54(_[0-9]+)*\1*$
>
> Alternatively what should also work: ^54(_[0-9]*)\1*$
>
> Optionally again the \1 as (\1)
>
>
> Cya
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
> Of Huizinga, Rene
> Sent: Wednesday, December 27, 2006 10:28 PM
> To: 'Bit Gossip'; ccielab@groupstudy.com
> Subject: RE: BGP Reg Exp
>
> Hmm, now I see...
>
> Ehrm, not certain if no solution is possible and mention that quickly.
> If it's really only for 1 REAL AS-depth behind AS54, how about:
>
> ^54(_[0-9]+)\1*$ ?
>
> :)
>
> That would match from left to right:
>
> - Something starting with AS54
> - 0 or more instances of something having '_' (space) directly
> followed with a set of [0-9] digits immediately behind
> - And now comes the trick... The '\1' indicates that it should match
> (ONLY) exactely again what it found in the last match between round
> brackets with the '*' that it should do this 0 or more times...
>
> It can be that for that last one you also need the '\1' between round
> brackets, but would need to check that out in the cmd-reference for
> regexp's... But this is what it comes down to... (So in that case:
> ^54(_[0-9]+)(\1)*$ )
>
> But check it out yourself, my last bookmark on this was:
> http://www.cisco.com/en/US/products/sw/iosswrel/ps1828/products_comman
> d_refe
> rence_chapter09186a00800ca541.html
>
> I'd say, paste it into a few lab-routers and check it out... Either
> with or without the round brackets it should work...
>
>
> Cya
>
> Rene.
>
>
> P.S.
>
> Even if it's wrong, I'd say 2 points for creativity... ;)
>
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
> Of Bit Gossip
> Sent: Wednesday, December 27, 2006 9:29 PM
> To: ccielab@groupstudy.com
> Subject: RE: BGP Reg Exp
>
> Hi Rene, GS,
> the original pb was: match all route of AS54 and its directly attached
> customers, where a customer could prepend once or more The trick here
> is that you don't know the AS of the customer before hand, so I agree
> that unless you list all possible ASs, there is no solution for this
> problem with a regular expression.... Luca.
>
>
> On Wed, 2006-12-27 at 20:48 +0100, Huizinga, Rene wrote:
> > Hi Luca,
> >
> >
> > Not certain if I understand your question correctly, but if you want
> > to accept all, with AND without prepending, try:
> >
> > ^54(_1234)+_
> >
> > Or ONLY when prepended:
> >
> > ^54(_1234)*_1234_
> >
> > In my understanding, this should be correct, correct me if I'm wrong
> > or please explain your question in case of misunderstandings...
> >
> >
> > Cya
> >
> > Rene.
> >
> > -----Original Message-----
> > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
> > Of Bit Gossip
> > Sent: Wednesday, December 27, 2006 8:23 PM
> > To: ccielab@groupstudy.com
> > Subject: RE: BGP Reg Exp
> >
> > I was wandering if it is possible to make the expression smarter so
> > that it can cope with the customer prepending once or more time;
> > something
> > like:
> > 54 1234 1234 1234
> > but not like
> > 54 1234 4321
> >
> > I couldn't come to any solution....
> >
> > Luca.
> >
> > On Wed, 2006-12-27 at 09:11 -0500, Scott Morris wrote:
> > > Both will work. Yours does 0 or more of the single character 0-9.
> > > The first does one or more, but makes the whole thing optional with
> > > the ? (0 or
> > > 1 of preceeding).
> > >
> > > Different logic, same result!
> > >
> > >
> > > Scott Morris, CCIE4 (R&S/ISP-Dial/Security/Service Provider)
> > > #4713,
> > > JNCIE #153, CISSP, et al.
> > > CCSI/JNCI-M/JNCI-J
> > > IPExpert VP - Curriculum Development IPExpert Sr. Technical
> > > Instructor smorris@ipexpert.com http://www.ipexpert.com
> > >
> > >
> > >
> > > -----Original Message-----
> > > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On
> > > Behalf
> > > Of JB
> > > Sent: Wednesday, December 27, 2006 4:59 AM
> > > To: ccielab@groupstudy.com
> > > Subject: BGP Reg Exp
> > >
> > > Hi all, question asks for a router to accept prefixes from BB1
> > > that
> > > have been originated by themselves and their directly connected
> customers.
> > >
> > > Solution says: ^54(_[0-9]+)?$
> > >
> > > I got ^54_[0-9]*$.
> > >
> > > I ran mine thru looking-glass and it "seems" to work. I would
> > > appreciate it if someone could explain the differences, if any,
> > > between the two to further my understanding.
> > >
> > > TIA,
> > >
> > > JB
> > >
> > > __________________________________________________________________
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