Subnetting

Addressing is a key function of Network layer protocols that enables data communication between hosts on the same network or on different networks. Internet Protocol version 4 (IPv4) provides hierarchical addressing for packets that carry our data.
Designing, implementing and managing an effective IPv4 addressing plan ensures that our networks can operate effectively and efficiently.
This chapter examines in detail the structure of IPv4 addresses and their application to the construction and testing of IP networks and subnetworks.
In this chapter, you will learn to:
• Explain the structure IP addressing and demonstrate the ability to convert between 8-bit binary and decimal numbers.
• Given an IPv4 address, classify by type and describe how it is used in the network.
• Explain how addresses are assigned to networks by ISPs and within networks by administrators.
• Determine the network portion of the host address and explain the role of the subnet mask in dividing networks.
• Given IPv4 addressing information and design criteria, calculate the appropriate addressing components.
Each device on a network must be uniquely defined. At the Network layer, the packets of the communication need to be identified with the source and destination addresses of the two end systems. With IPv4, this means that each packet has a 32-bit source address and a 32-bit destination address in the Layer 3 header.
These addresses are used in the data network as binary patterns. Inside the devices, digital logic is applied for their interpretation. For us in the human network, a string of 32 bits is difficult to interpret and even more difficult to remember. Therefore, we represent IPv4 addresses using dotted decimal format.