Network addresses were originally defined by the internet the Internet community in five address classes. These classes were defined in order to accommodate networks of varying sizes. TCP/IP supports class A, B, and C addresses assigned to hosts. These classes define which bits are used for the network ID and which bits are used for the host ID. It also defines the possible number of networks and the number of hosts per network.
Class A addresses are assigned to networks that have a very high number of hosts. The first 8-bits make up the network ID while the remaining 24-bits are used to define the host ID. This affords a network with class A addresses to have up to 126 unique networks and over 16,000,000 hosts per network. This is ...view middle of the document...
This class has close to an even amount of networks to hosts per network ratio. Whereas class C addresses give you more networks than hosts.
A class C address is assigned to networks that are small and don’t have very many hosts. The first three bits of this address class are assigned the binary code 1 1 0 respectfully. Then next 21-bits are used to define the network ID. The last 8-bits are used to define the host ID. This allows for the largest amount of networks but the fewest amounts of hosts within those networks. A little over 2.1 million networks can be made in the address class however only 254 hosts are allowed per network.
Other types of address are reserved for special use. Class D addresses are reserved for multicast capable hosts. RFC addresses are used for private networks. Martian addresses are addresses are invalid addresses because they have either been spoofed by a hacker or have not been properly assigned to a network load. These addresses can be added to an address pool that has not been assigned by the IANA. The addresses are unreserved and can be used by hackers to send false denial of service ploys.
 G. E. Clarke, "Chapter 4 - Introduction to TCP/IP," in CCENT Certification All-In-One For Dummies, John Wiley & Sons, 2011.
 R. Shimonski, "Chapter 7 - TCP/IP and Routing," in CompTIA Network+ Certification Study Guide, Syngress Publisher, 2009.
 Microsoft, "Address Classs," Microsoft, 2014. [Online]. Available: http://technet.microsoft.com/en-us/library/cc940018.aspx. [Accessed 17 April 2014].
 Techopedia, "Martian Address," Techopedia, 2014. [Online]. Available: http://www.techopedia.com/definition/25075/martian-address. [Accessed 17 April 2014].