SubNet: IP subnetting algorithms
  Copyright (C) 2002 German Viscuso
  E-mail: netquake@netquake.com.ar
 
  This program is free software; you can redistribute it and/or modify
  it , under the terms of the GNU General Public License as published
  by the Free Software Foundation; either version 2 of the License,
  or (at your option) any later version.
 
  This program is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
  See the GNU General Public License for more details.
 
  You should have received a copy of the GNU General Public License
  along with this program; if not, write to the Free Software
  Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.

Given a valid IP address, SubNet let's you calculate:

-A binary representation of the address
-Network class
-Network bits used
-Subnet bits allocated
-Netmask
-Number of possible subnets
-Subnet segments plus broadcast address
-Host bits used (bits allocated to address hosts)
-Number of hosts per subnet

(you must also supply the number of subnets you want
or a netmask in / notation which represents the number
of bits allocated for network plus bits for subnets)
 

Test the applet
 

SubNet: IP subnetting algorithms
by German Viscuso netquake@netquake.com.ar