In this chapter, the author will first present in Section 3.1 an overview of IP addresses with various types and addressing mechanisms. The first version of IP addresses, namely, IP version 4 (IPv4) will be discussed in Section 3.2 followed by various mechanisms for dividing the network with subnetting in Sections 3.3 and 3.4 as well as how to group the small networks via supernetting in Section 3.5. A brief introduction of the extended version of IP addressing called IP version 6 (IPv6) will be described in Section 3.6 along with discussions for further readings.