Know About Classful Addressing in IP Address & Selection of NetId & HostId

In the digital realm of interconnected devices and data communication, IP addresses form the backbone of the internet. These numerical labels serve as unique identifiers, facilitating seamless data exchange between devices across the globe. IP addresses are a fundamental concept in networking, and classful addressing was the initial method used to manage IP address allocation. In this article, we will demystify IP addresses, explain the concept of classful addressing, and delve into how NetId and HostId are selected with the help of examples.

Understanding IP Addresses

An IP address, short for Internet Protocol address, is a numeric label assigned to each device connected to an IP-based network. It serves two primary purposes: identifying the host or network interface and providing the location of the host in the network. IP addresses are essential for routing data packets across the internet, ensuring they reach their intended destinations.

Concept of Classful Addressing

Classful addressing was the original method of IP address allocation, based on five classes: A, B, C, D, and E. Each class has a fixed size of network and host portions, and the class to which an IP address belongs determines how the NetId (network identifier) and HostId (host identifier) are selected.

Selecting NetId and HostId

Let’s take a closer look at how NetId and HostId are selected for each class with the help of examples:

Class A Address:

• Example IP Address: 10.10.10.10
• Class A addresses start with a binary “0” in the first bit. The NetId occupies the first 8 bits (the first octet), and the remaining 24 bits are for the HostId.

Class B Address:

• Example IP Address: 172.16.10.10
• Class B addresses start with the binary sequence “10” in the first two bits. The NetId occupies the first 16 bits (the first two octets), and the remaining 16 bits are for the HostId.

Class C Address:

• Example IP Address: 192.168.1.10
• Class C addresses start with the binary sequence “110” in the first three bits. The NetId occupies the first 24 bits (the first three octets), and the remaining 8 bits are for the HostId.

Class D and E Addresses: Class D addresses (starting with “1110” in the first four bits) are reserved for multicast groups, and Class E addresses (starting with “1111” in the first four bits) are reserved for experimental purposes, with no specific NetId and HostId assignment.

Advantages of Classful Addressing:

• Classful addressing allowed for straightforward address allocation, making it easier to manage IP address spaces in the early days of the internet.
• It provided a basic level of hierarchy, facilitating efficient routing and addressing of networks.

Disadvantages of Classful Addressing:

• The rigid structure of classful addressing led to inefficient use of IP address space, especially for Class A and B addresses, where most organizations did not require such large address ranges.
• With the exponential growth of the internet, classful addressing quickly ran out of available IP addresses, necessitating the development of classless addressing (CIDR) and IPv6.

Conclusion:

IP addresses are the lifeblood of the internet, serving as unique identifiers for devices and enabling seamless data communication. Classful addressing was an early method used to allocate IP addresses, based on fixed classes with predetermined NetId and HostId portions. While classful addressing provided a basic hierarchy for IP address management, it eventually proved inadequate for the growing demands of the internet. Consequently, classless addressing (CIDR) and IPv6 were introduced to address the limitations of classful addressing and accommodate the ever-expanding digital landscape.