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Re: IP range to CIDR
From: Alex van den Bogaerdt (alex
ergens.op.het.net)
Date: Mon Jan 26 2004 - 17:10:34 CST
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On Mon, Jan 26, 2004 at 04:01:50PM -0700, Cameron Knowlton wrote:
> I was wondering if anyone knows of a web page or a Mac OS application that can convert from IP ranges to CIDR addresses, e.g.:
>
> 200.41.0.0-200.41.127.255 --> a.b.c.d/x
If nothing shows up, and if you can write your own:
Range from "x" upto and including "y", properly aligned.
r=(x xor y)
add one
shift right until r==1, count number of shifts
subtract from 32.
Example
200.41.0.0
200.41.127.255
-------------- xor
0.0.127.255
0.0.127.255
1
----------- +
0.0.128.0
binary:
00000000 00000000 10000000 00000000
15 shift-right,
32-15=17 --> 200.41.0.0/17
HTH
Alex
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