Re: IP BGP REGEXP

Hi Vincent,

To catch the difference better to test those regex on the route servers.

HTH,

Aliou

On 7 January 2012 05:30, Yuri Bank <yuribank_at_gmail.com> wrote:

> For AS54 and its directly connected customers, either of those regular
> expressions would work.
>
> They're just formulated with slightly different logic. The only difference
> would be maybe the low level processing by the regex engine.
>
> -Yuri
>
> On Fri, Jan 6, 2012 at 8:20 PM, Vincent Tay <vtay.75_at_gmail.com> wrote:
>
> > Hi,
> >
> > If i want to match routes originated from 54 and ONLY directly connected
> > customers for example 10 254 and not 10 254 253, should i use
> ^54_[0-9]*$
> > or ^54(_[0-9]+)?$. The solution state the second latter but i search the
> > terminal services appendix documentation and it is the first latter. Can
> > you explain the two? Thanks.
> >
> > Regards.
> >
> > On Sat, Jan 7, 2012 at 12:08 PM, Vincent Tay <vtay.75_at_gmail.com> wrote:
> >
> >> Thanks. Got it.
> >>
> >>
> >> On Sat, Jan 7, 2012 at 2:55 AM, Yuri Bank <yuribank_at_gmail.com> wrote:
> >>
> >>> 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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> >>>>
> >>>>
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> >>>>
> >>>>
> _______________________________________________________________________
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>
>
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>
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Received on Sat Jan 07 2012 - 09:36:55 ART