Re: IP BGP REGEXP

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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Received on Fri Jan 06 2012 - 21:30:13 ART