From: Brian McGahan (brian@xxxxxxxxxxxxxxx)
Date: Sat Aug 24 2002 - 14:28:58 GMT-3
Chang,
What Brian was referring to was in the case of an AS set. It is
a possibility that an AS along the way who is learning prefixes that
were originated in AS 10 is aggregating them, and including the AS set.
Since I'm not checking for any instances of 10 in an AS set, Brian is
technically correct.
However, since AS set is an ordered set, there is no way to
check whether or not the prefixes were actually originated in AS 10, or
merely transited through AS 10 before aggregation.
On a side note, Chang, you mentioned "I know we can replace
(.*_) with (.*) and still get the same result." Actually this is not
the case. If you remove the _, you would match the case of: 1000 100
x10, where x is any number. The _ ensures that the AS path ends with
exactly 10.
HTH
Brian McGahan, CCIE #8593
Director of Design and Implementation
brian@cyscoexpert.com
CyscoExpert Corporation
Internetwork Consulting & Training
http://www.cyscoexpert.com
Voice: 847.674.3392
Fax: 847.674.2625
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
ying c
Sent: Saturday, August 24, 2002 10:56 AM
To: Brian Dennis; 'Brian McGahan'; msnyder@revolutioncomputer.com;
'Bauer, Rick'
Cc: ccielab@groupstudy.com
Subject: RE: regexp fun (multiple solutions)
Brian,
I even could not come up a single case. Take the first
solution and break them down:
^1000_(.*_)?100_(.*_)?10$
? = 0 0 => ^1000_100_10$
? = 0 1 => ^1000_100_(.*_)10$
? = 1 0 => ^1000_(.*_)100_10$
? = 1 1 => ^1000_(.*_)100_(.*_)10$
I know we can replace (.*_) with (.*) and still get
the same result, but I think they pretty much cover
all the ground, so what exactly is missing?
Thanks,
Chang
--- Brian Dennis <brian@5g.net> wrote:
> Brian,
> You said "all routes originated in AS 10, passed
> through AS 100, and
> learned from AS 1000", right? There are cases where
> your regular
> expressions won't meet the criteria ;-)
>
> Brian Dennis, CCIE #2210 (R&S/ISP Dial)
>
> -----Original Message-----
> From: nobody@groupstudy.com
> [mailto:nobody@groupstudy.com] On Behalf Of
> Brian McGahan
> Sent: Thursday, August 22, 2002 9:06 PM
> To: msnyder@revolutioncomputer.com; 'Bauer, Rick'
> Cc: ccielab@groupstudy.com
> Subject: RE: regexp fun (multiple solutions)
>
> Try these:
>
> ^1000_(.*_)?100_(.*_)?10$
>
> ^1000_(|.*_)100_(|.*_)10$
>
> ^1000_([0-9]+_)*100_([0-9]+_)*10$
>
> Brian McGahan, CCIE #8593
> Director of Design and Implementation
> brian@cyscoexpert.com
>
> CyscoExpert Corporation
> Internetwork Consulting & Training
> http://www.cyscoexpert.com
> Voice: 847.674.3392
> Fax: 847.674.2625
>
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