[c-nsp] Calculate wildcard..

[Todd, Douglas M.]

This might help in addition to what Bill sent:

http://blog.internetworkexpert.com/2007/12/26/q-how-do-i-compute-complex-wildcar
d-masks-for-access-lists/

 

-----Original Message-----
From: cisco-nsp-bounces at puck.nether.net
[mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of bill fumerola
Sent: Sunday, June 22, 2008 2:39 AM
To: almog ohayon
Cc: cisco-nsp at puck.nether.net
Subject: Re: [c-nsp] Calculate wildcard..

On Sat, Jun 21, 2008 at 07:41:18PM +0300, almog ohayon wrote:
> Q : when i have couple of address that i need to know their common 
> wildcard, i XOR them and i get excellent result but
>      how can i know that i'm not overlapping any other addresses ??

a wildcard will match 2^x addresses where x= the number of bits set.

examples:
0.0.0.1 = 0 0 0 1 = 2 addrs 
   10.0.0.0 10.0.0.1 = 10.0.0.0 0.0.0.1
0.0.0.3 = 0 0 0 11 = 4 addrs
   10.0.0.0 10.0.0.1 10.0.0.2 10.0.0.3 = 10.0.0.0 0.0.0.3
0.0.0.6 = 0 0 0 110 = 4 addrs
   10.0.0.0 10.0.0.2 10.0.0.4 10.0.0.6 = 10.0.0.0 0.0.0.6
0.1.0.1 = 0 1 0 1 = 4 addrs
   10.0.0.0 10.1.0.0 10.0.0.1 10.1.0.1 = 10.0.0.0 0.1.0.1


-- bill
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