Classless Addressing (Part 1)

Summary

This lecture discusses the limitations of classful IP addressing, which categorizes addresses into five classes and often leads to IP address wastage. It highlights the drawbacks, such as lack of flexibility, inefficient address use, and increased routing table entries, which necessitate the transition to classless addressing. Classless addressing allows for a more efficient and flexible allocation of IP addresses based on actual network requirements, reducing waste and improving routing performance.

Takeaways

• 📚 Classful addressing in IPv4 is divided into five classes: A, B, C, D, and E, with A, B, and C being the most commonly used for general purposes.
• 🚀 In classful addressing, a Class C network can support up to 254 hosts, but if more hosts are needed, a larger class like B is required, which can support up to 65,534 hosts.
• 🔢 The script highlights a specific example where a requirement of 300 devices leads to the necessity of using Class B, resulting in the waste of 65,234 IP addresses.
• 🏢 Large organizations face the drawback of classful addressing due to the lack of flexibility in internal address allocation, as they are assigned large blocks of addresses that may not match the network structure.
• 📉 Classful addressing leads to inefficient use of address space, as only three classes are used for general purposes, and the existence of three block sizes can lead to waste.
• 🌐 The growth of the internet requires routers to handle more routing table entries, which can cause performance issues due to the proliferation of routing table entries in classful addressing.
• 🚫 One of the main drawbacks of classful addressing is the lack of internal address flexibility, inefficient use of address space, and the increase in routing table entries.
• 🔄 The transition from classful to classless addressing is necessary to address the issues of IP address wastage and routing table inefficiencies.
• 💡 Classless addressing allows for the creation of subnet masks based on the actual needs of the network, enabling more efficient use of IP addresses.
• 🌟 In classless addressing, networks can be designed to use IP addresses sparingly, reducing waste compared to classful addressing.
• 🎓 The lecture concludes by emphasizing the understanding of the drawbacks of classful addressing and the advantages of classless addressing for efficient IP address utilization.

Q & A

What is classful addressing in IP networking?

Classful addressing refers to the system of IP version 4 (IPv4) where there are five classes of addresses: A, B, C, D, and E, with classes A, B, and C being used for general purposes. Each class has a fixed subnet mask and a maximum number of hosts it can support.

What is the maximum number of hosts that can be supported in a Class C network?

A Class C network can support up to 254 hosts.

Why might Class B addressing be inefficient for a network that requires only 300 devices?

Class B addressing is inefficient for a network requiring only 300 devices because it can support up to 65,534 hosts, which means that 65,234 IP addresses would be wasted.

What is the main drawback of classful addressing when it comes to IP address allocation?

The main drawback of classful addressing is the inefficient use of IP address space due to the fixed subnet masks and the large blocks of addresses that may not match the underlying network structure.

How does classful addressing affect the routing table entries in routers?

Classful addressing can lead to the proliferation of routing table entries as routers need to store more entries to handle the routing of IP datagrams, which can cause performance problems.

What is the maximum number of hosts that can be supported in a Class A network?

A Class A network can support 1,677,214 hosts.

How does classless addressing address the issue of IP address wastage compared to classful addressing?

Classless addressing allows for the creation of custom subnet masks and more efficient use of IP addresses based on the actual requirements of the network, thus reducing wastage.

What is one of the main benefits of classless addressing over classful addressing?

One main benefit of classless addressing is the lack of internal address flexibility, allowing for a better match between the assigned address blocks and the structure of the underlying internal network.

Why is it necessary to migrate from classful to classless addressing?

It is necessary to migrate from classful to classless addressing to address the drawbacks of classful addressing, such as lack of flexibility, inefficient use of address space, and the proliferation of routing table entries.

Can you give an example of how classless addressing allows for more efficient IP address usage?

In classless addressing, if a network requires only 25 computers, it can create a custom subnet mask that allows for exactly 25 usable IP addresses, thus avoiding the wastage of addresses that would occur with classful addressing.

What is the impact of classless addressing on the size of routing tables in routers?

Classless addressing can potentially reduce the size of routing tables by allowing for more efficient allocation of IP addresses, which in turn can reduce the number of entries required in routing tables.