From: Tim Fletcher (groupstudy@fletchmail.net)
Date: Sun Aug 31 2003 - 17:51:11 GMT-3
You RE would not match "123 456" or "456 123", as well as many other AS strings that do meet the criteria, because if the "[0-9]+_" at the end of each section. If you eliminate that, it should work.
(_123_([0-9]+_)*(456_)+)|(_456_([0-9]+_)*(123_)+)
But we can clean it up quite a bit, which would make it simpler to read.
First of all, the outer parenthesis don't do anything here,
_123_([0-9]+_)*(456_)+|_456_([0-9]+_)*(123_)+
Next, the (456_)+ and (123_)+ mean we can have 1 or more of these strings. Since we only need 1 to meet the criteria, we can simplify this as well.
_123_([0-9]+_)*456_|_456_([0-9]+_)*123_
Lastly, we what's between the 2 ASs we are looking for, so we could replace [0-9] with ".".
_123_(.+_)*456_|_456_(.+_)*123_
-Tim Fletcher
At 12:55 AM 8/30/03 -0400, asadovnikov wrote:
>Typo corrected:
> (_123_([0-9]+_)*(456_)+[0-9]+_)|(_456_([0-9]+_)*(123_)+[0-9]+_)
>
>-----Original Message-----
>From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
>asadovnikov
>Sent: Saturday, August 30, 2003 12:45 AM
>To: 'Nathaly Landry'
>Cc: ccielab@groupstudy.com
>Subject: RE: regular expression
>
>
>If you look at Internet routing table you will be surprised how many routes
>of that kind are actually there. Prepending AS path with a number of the AS
>is a standard Internet practice of announcing "backup" route. I.e. if my AS
>is 456, and I am dual-homed to 123 and 124, and I prefer inbound traffic to
>come via 124, I will send my prefixes 'as is' to 124 and prepend them with
>456 several times when sending to 123. So say I am announcing 10.0.0.0/8
>(which I obviously would not to Internet), then the following to entries
>will be seen (from upstream):
>
>10.0.0.0/8 124 456
> 123 456 456 456 456 456
>
>The following modification of reg-exp should take care of this situation:
> (_123_([0-9]+_)*(456_)+[0-9]+_)|(_456_([0-9]+_)*(123)+_[0-9]+_)
>
>I have to say that now I am stretching my abilities to do reg-exp without
>testing; still to lazy to try :)
>
>Best regards,
>Alexei
>
>-----Original Message-----
>From: Nathaly Landry [mailto:lnathaly@cisco.com]
>Sent: Friday, August 29, 2003 11:13 PM
>To: 'asadovnikov'
>Subject: RE: regular expression
>
>
>Thank you
>
> If you have an as-path that has 123 456 456, one might have more
>pressing issues than worrying about reg exp!! ;-)
>
>nat
>
>-----Original Message-----
>From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
>asadovnikov
>Sent: Friday, August 29, 2003 10:24 PM
>To: 'Cristian Henry H'; 'Nathaly Landry'
>Cc: 'Chepuri Roshan'; 'Ram Shummoogum'; ccielab@groupstudy.com
>Subject: RE: regular expression
>
>
>I am a little to lazy right now to try it but I think the following will
>work:
> (_123_([0-9]+_)*456_[0-9]+_)|(_456_([0-9]+_)*123_[0-9]+_)
>
>([0-9]+_)* - in the middle will match zero and more AS numbers between
>123 & 456, and
>[0-9]+_ - at the end will ensure that the 123/456 is not the last AS
>number
> (it would match though 123 456 456, which is only
>limitation of this
> reg-exp)
>
>-----Original Message-----
>From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
>Cristian Henry H
>Sent: Thursday, August 28, 2003 9:36 AM
>To: Nathaly Landry
>Cc: 'Chepuri Roshan'; 'Ram Shummoogum'; ccielab@groupstudy.com
>Subject: Re: regular expression
>
>
>My opinion
>
>^([1-9]+_)*(123|456)_([1-9]+_)*(123|456)_([1-9]+_)*$
>
>Nathaly Landry ha escrito:
>>
>> Cleaning up my folder, did not see an answer for that one, I
>> think that the reg expression is: Reg exp to only accept routes that
>> have transitted thru AS 123 AND AS 456
>>
>> ^((.+_)*123(_.+)*_456(_.+)*)$|((.+_)*123(_.+)*_456(_.+)*$)
>>
>> Any idea?
>> Nat
>>
>> -----Original Message-----
>> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
>> Of Chepuri Roshan
>> Sent: Thursday, February 20, 2003 11:55 PM
>> To: Ram Shummoogum
>> Cc: ccielab@groupstudy.com
>> Subject: Re:
>>
>> Try _[1,4][2,5][3,6]_
>>
>> At 10:34 PM 2/20/2003 -0500, Ram Shummoogum wrote:
>> >Hi ALL:
>> >
>> >
>> >I need some help on this BGP regular expression.
>> >
>> >
>> >Make a router only accept routes that has transit AS 123 and AS 456.
>
>> >The keyword here is "and" and not or.
>> >
>> >
>> >Ex: {34 5 6 456 7 99 123 88}
>> > {45 123 89 456 7}
>> >
>> >
>> >
>> >
>> >
>> >I know "OR" is | but what is AND.
>> >
>> >
>> >
>> >
>> >
>> >Thanks for your help
>> >
>> >
>> >RAM
>>
>> ______________________________________________________________________
>> _
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>--
>Cristian E. Henry
>REUNA
>
>E-mail: chenry@reuna.cl
>Fono: 56-2-3370336
>
>
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