Internet Protocol Tutorial

why subnet?

Well, think of each room in your home as a "subnet" of the overall space underneath the roof. By "subnetting" the house, you get more manageable sections that you can specialize it's use. Same thing with networks. You want to subnet the network so that you can have one subnet for the servers, one subnet for the clients, one subnet for wireless, and so on. Now do you see WHY you want to subnet?

http://compnetworking.about.com/od/tcpiptutorials/a/ipaddrnotation.htm

How Subnet Mask increase the total number of IP?

IP address: 192.168.1.233 

Subnet Mask: 255.255.255.0 (C class)

IP address: 192.168.1.233 

Subnet Mask: 255.255.0.0 (B class)

通过这两组ip访问到的是两个完全不同的hosts, 虽然IP address 是一样的.