What Subnet is.?
Sub Network or Subnet is a logical division of IP Network and the Practice of dividing networks into multiple(Two or More) subnetworks (or) creating of networks within a network is called Subnetting. Division of a network into Subnetworks is helps to maintain a clean separations within a network, security.
Subnetting Allows a single IP Address for a complete organization (Class A/Class B/ Class C) to have different subnetworks, thus allowing several physical networks with in the organization. IP Adresses in Classes are written using decimal numbers separated by decimal points. This is nothing but dotted decimal notation of expressing IP addresses. The different classes of IP addresses is explained in detail in the page mentioned here. http://www.examguides.com/CCNA/cisco-ccna-6.htm. It Explains detailed about Subnetting, Division of IP Address Classes with Examples for easy understanding.