Re: IP BGP REGEXP

Actually, both regular expressions will match routes originated by AS54

The important distinction between these two regular expressions is that the
first will match *any* AS_PATH_SEQ that starts with AS54. The second
regular expression will match any AS_PATH_SEQ that starts with AS54,
followed by *one* or *none* additional AS numbers.

_ underscore will match space or end of string

-Yuri

On Fri, Jan 6, 2012 at 5:04 AM, Keller Giacomarro <keller.g_at_gmail.com>wrote:

> They are similar, but not the same.
>
> The first says...
> Match from the start of the line
> Match 54
> Match a space
> I don't care about the rest
>
> The second says...
> Match from the start of the line
> Match 54
> Match a space
> Match a number 0 to 9, one or more times (as few characters as needed,
> ungreedy)
> I don't care about the rest
>
> The big difference is that the second regex will require that the next AS
> must be a normal AS number, 0 to 9. If it is an AS_SET next (parenthesis),
> or a confederacy (squiggly brackets) next, the second regex will not match
> but the first will.
>
> Also, note that neither regex will match for AS54-originated routes, as you
> a requiring a space after 54.
>
> When I'm trying to create regexes, http://gskinner.com/RegExr/ is my best
> friend.
>
> Keller Giacomarro
> keller.g_at_gmail.com
>
>
> On Fri, Jan 6, 2012 at 5:42 AM, Vincent Tay <vtay.75_at_gmail.com> wrote:
>
> > Hi all,
> >
> > Any differences between the below BGP regexp?
> >
> > ^54_ and ^54(_[0-9]+)?$ to match originated from AS54 and its directly
> > connected customers?
> >
> >
> > Blogs and organic groups at http://www.ccie.net
> >
> > _______________________________________________________________________
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>
>
> Blogs and organic groups at http://www.ccie.net
>
> _______________________________________________________________________
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Received on Fri Jan 06 2012 - 10:55:59 ART