Re: BGP Regular Expression

This make sense..i got it...I tested it ..works like that

Thanks guys..

On Mon, May 24, 2010 at 12:23 AM, Ruhann <groupstudy_at_ru.co.za> wrote:

> ^  matches the beginning of a line (everything in
> life has a start)
>
> [0-9]  includes any number between 0 and 9
>
> + after [0-9]  means any number between 0 and 9 must be repeated 1 or
> more times.
>
> ( )  groups multiple expressions together.
>
> _  Underscore will match any Delimiter (including
> beginning, end, space, tab, comma)
> In this example it will most likely match a SPACE.
>
> \1  references the previous Parenthesis ([0-9]+)
>
> (_\1)  means that any number 0-9 may repeat x amount of times
> preceded by a SPACE, or beginning-of line
>
> (_\1)*  the * means the previous statement can be repeated zero
> or more times.
>
> $  in this case: run the loop from the previous statement
> until the number sequence is followed by a end-of-line.
>
>
> The short version :
> If used in a as-path access-list, it will match ANY neighboring ASN
> while allowing that AS to prepend their ASN x amount of times.
>
> HTH
> --
> <ruhann>
> www.routing-bits.com
>
>
> On Mon, May 24, 2010 at 8:27 AM, Raghav Bhargava
> <raghavbhargava12_at_gmail.com> wrote:
> > Hi Experts,
> >
> > Can anyone please explain this Regular Expression:
> >
> > ^([0-9]+)(_\1)*$
> >
> >
> > --
> > Warm Regards
> > Raghav
> >
> >
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> >
> >
> >
> >
> >
>
>
>
> --
> <ruhann>
> www.routing-bits.com
>

--
Warm Regards
Raghav
Blogs and organic groups at http://www.ccie.net