Here is a site for a CIDR (Classless Inter Domain Routing) calculator: http://www.subnet-calculator.com/cidr.php First you have to know how many PC's you want on your subnet, what you want your IP address to be and then you can figure out your subnet mask which is the source of subnetting. If you need help, let me know. I am also attaching a worksheet I created. CIDR.doc