Re: Regular Expressions ......

["Yu Ning" <yuning () cndata com>]

Hi,

Sorry for pick up the historic thread. But why not a more simple and
clear one?

ip as-path access-list 1 permit ^[0-9]+$
ip as-path access-list 2 permit ^([0-9]+) ([0-9]+)$
ip as-path access-list 3 permit ^([0-9]+) ([0-9]+)([0-9]+)$
ip as-path access-list 4 permit .*

It's quite clear, and you can expand it to whichever level you want.
Correct me if i were wrong.

regards,

Yu Ning
-------------------------------------------
(Mr.) Yu(2) Ning(2)
ChinaNet Backbone Operation
Networking Dep.,Datacom Bureau
China Telecom.,Beijing(100088),P.R.C
+86-10-66418105/66418121/66418123(fax)
-------------------------------------------

----- Original Message ----- 
From: "Peter T. Whiting" <pwhiting () fury ittc ukans edu>
To: "Ally Gudgeon" <alison.gudgeon () kingston-internet net>
Cc: <nanog () merit edu>
Sent: Friday, May 26, 2000 7:40 PM
Subject: Re: Regular Expressions ......


> I see two problems.
>
> 1. _ matches the beginning of the string, the end of the string,
> space, braces, comma, underscore or parentheses.  What you probably
> wanted in your regexp is a normal space. 
>
> 2. * matches zero or more of the previous pattern, what you probably
> wanted was a + (you want to force it to have at least one
> digit.)
>
> Fixing either one of these will produce the results you are
> looking for.  I recommend  fixing both.  Also, note that you
> can stack "beginning of string" or "end of string".  The 
> following produce the same result.
>
> sho ip bgp reg ^_^^[0-9]*^^_^^_^[0-9]*$_$$
> sho ip bgp reg ^_^^[0-9]*$___$__[0-9]*$$_$
> sho ip bgp reg ^[0-9]*$
>
> the point?  Be careful with * and _.
>
> pete
>
>
>
> On Fri, May 26, 2000 at 10:07:50AM +0100, Ally Gudgeon wrote:
> > Hi All,
> >
> > I am having a few problems getting my BGP filtering to work - and am
> > experiencing some strange results..
> >
> > I have two routers connected to a peering point, we have decided that we
> > want to set local preferences of
> >
> > 110 to 1-deep AS-paths (as-path ACL 1)
> > 100 to 2-deep AS-paths (as-path ACL 2)
> > and 90 to 3-deep AS-paths (as-path ACL 3)
> > and to not accept 4-deep AS-paths (as-path ACL 4)
> >
> > I have the following as-path ACLs to try to set that and am using route
> > maps.
> >
> > ip as-path access-list 1 permit ^[0-9]*$
> > ip as-path access-list 2 permit ^[0-9]*_[0-9]*$
> > ip as-path access-list 3 permit ^[0-9]*_[0-9]*_[0-9]*$
> > ip as-path access-list 4 permit .*
> >
> > This appears to have failed miserably....It is not setting local prefs
> > correctly if they are 3-deep and have a repetition of an AS number it sees
> > it as 4-deep
> > If they are 4 AS's deep it doesn't apply a local preference but if it knows
> > it from our other core router it sets a local pref of 100 but prefers the
> > direct route?
> >
> > (ALSO: If I do a sh ip bgp reg ^[0-9]*_[0-9]*$ it lists both 1-deep and
> > 2-deep AS's....surely it should just list 2-deep?)
> >
> > Any help would be greatly appreciated!......
> >
> > Thanks in advance..
> >
> >
> > Ally
> >
> >
> > email - alison.gudgeon () kingston-internet net
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