What is classful routing?

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What is Classful Routing?
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Classful routing is one of the oldest routing protocols used in computer networks. It was primarily used in the early days of the internet when there was a limited number of networks. Classful routing is based on the concept of dividing IP addresses into different classes, namely Class A, Class B, and Class C, to determine the network boundary.

IP Address Classes

The IP address is a unique identifier for devices connected to a network. In classful routing, the IP address is divided into three classes:

1. Class A: The first octet of the IP address is used to identify the network, while the remaining three octets are used to identify hosts. Class A addresses are used for large networks and can support a large number of hosts. The range of Class A addresses is from 1.0.0.0 to 126.0.0.0.

2. Class B: The first two octets of the IP address are used to identify the network, while the remaining two octets are used to identify hosts. Class B addresses are used for medium-sized networks. The range of Class B addresses is from 128.0.0.0 to 191.255.0.0.

3. Class C: The first three octets of the IP address are used to identify the network, while the remaining octet is used to identify hosts. Class C addresses are used for small networks. The range of Class C addresses is from 192.0.0.0 to 223.255.255.0.

Routing in Classful Routing

In classful routing, the routing table stores information about the network addresses. When a packet is received, the router checks the destination IP address and looks for a match in the routing table. If a match is found, the packet is forwarded to the corresponding network. However, classful routing does not carry detailed subnet information, which limits its flexibility.

One of the drawbacks of classful routing is its inability to support Variable Length Subnet Masking (VLSM). VLSM allows for the allocation of different subnet sizes within a network, which classful routing cannot accommodate. This limitation led to the development of classless routing protocols, such as Classless Inter-Domain Routing (CIDR).

Conclusion

While classful routing was widely used in the past, its limitations have made it less prevalent in modern computer networks. The introduction of classless routing protocols has provided more flexibility and efficiency in routing. Understanding classful routing is still important for network professionals to comprehend the evolution and development of routing protocols.

What is classful routing? – one of the routing protocols