North American Network Operators Group
Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical

Re: As-Path filtering based on ranges, not regex

  • From: Brett Frankenberger
  • Date: Fri Jan 17 12:55:13 2003 
On Fri, Jan 17, 2003 at 12:10:59PM -0500, Andy Johnson wrote:
> 
> Vincent,
> 
>     I'm fairly certain it can match a range, just as you yourself posted you
> could do. There is no difference between using a range to find 0-9, than
> there is finding 64512-65535. 

There is in regular expressions. 

>So your line would look something like this:
> 
>     ip as-path access-list 150 permit _[64512-65535]$

[0123] is a one-character regular expression matching the digit 0, 1,
2, or 3.

[3-5] is a one-character regular expression matching 3, 4, or 5.

[64512-65535] is a one-character regular expression matching
1,2,3,4,5 or 6.  (It's way more complex than it needs to be, of course. 
You've got 6 listed in there twice; five is listed 4 times and also
included in the 2-6 range, and so on.)

So your expression above is going to match paths ending with AS 1, 2,
3, 4, 5, or 6.

     -- Brett