Difference between Classful Routing and Classless Routing

When it comes to routing protocols in computer networks, there are two main types of protocols that are commonly used: classful routing and classless routing. While both protocols are used for similar purposes, there are some significant differences between them that can have an impact on the performance and functionality of the network.

Classful Routing

Classful routing is one of the oldest types of routing protocols, which was first introduced in the early days of computer networking. In this type of routing protocol, the network is divided into different classes, and each class is assigned a predetermined range of IP addresses. These classes are known as Class A, Class B, and Class C.

In classful routing, the router makes decisions about routing based on the class of the IP address. This means that the router only considers the class of the IP address, rather than the actual subnet mask, when making routing decisions.

Classful routing is not very flexible, as it does not allow for the use of variable-length subnet masks, which are used to divide a network into smaller subnets. This means that the network can become inefficient, as the router must use larger subnets than it needs to in order to accommodate the lack of flexibility in the routing protocol.

Here is a sample code for classful routing:

router ospf 1
network 10.0.0.0 0.255.255.255 area 0
network 172.16.0.0 0.15.255.254 area 0
network 192.168.0.0 0.0.255.255 area 0

This code tells the router to create three networks: one for the Class A network 10.0.0.0, one for the Class B network 172.16.0.0, and one for the Class C network 192.168.0.0.

Classless Routing

Classless routing is a more modern approach to routing than classful routing. In this type of routing protocol, the subnet mask is taken into account in routing decisions, rather than just the class of the IP address.

This means that variable-length subnet masks can be used, which allows for more efficient use of the network’s resources. The routing protocol can also be more flexible, as the router can make more granular routing decisions based on the subnet mask.

Here is a sample code for classless routing:

router ospf 1
network 10.0.0.0 0.255.255.255 area 0
network 172.16.0.0 0.15.255.254 area 0
network 192.168.0.0 0.0.255.255 area 0

This code is similar to the code for classful routing, but it also specifies the subnet mask for each network. This allows for more granular routing decisions, as the router can take into account the specific subnet of each network when making routing decisions.

Conclusion

In summary, while both classful routing and classless routing are used for similar purposes, classless routing is generally considered to be the more efficient and flexible option. By allowing for the use of variable-length subnet masks, classless routing can make more granular routing decisions, which allows for more efficient use of network resources.