Mengenal Classless Inter-Domain Routing (CIDR) | Network Fundamental Learning Series #9

Summary

In this video, the concept of Classless Inter-Domain Routing (CIDR) is explored, continuing from a previous lesson on Classful Addressing. CIDR is presented as a more efficient approach to IP addressing, where subnet masks are determined using prefix notation (e.g., /24) instead of class-based addressing. The video discusses the issues with Classful Addressing, such as wasted IP addresses, and introduces subnetting as a solution. Detailed examples and calculations of network, broadcast, and usable host addresses are provided, offering viewers practical knowledge for optimizing network design and management using CIDR.

Takeaways

• 😀 Classless Interdomain Routing (CDR) is introduced as an advanced concept, following the classful addressing video, focusing on IP address management and subnetting.
• 😀 In the previous video, the concept of classful addressing was covered, which classifies IP addresses into classes A, B, and C based on their ranges.
• 😀 A key problem with classful addressing is the inefficient use of IP addresses, especially when large blocks of IPs are allocated to small networks.
• 😀 Subnetting is proposed as a solution to the inefficiency of classful addressing, breaking down large IP blocks into smaller, more manageable subnets.
• 😀 The benefits of subnetting include reducing broadcast traffic, easier network management, more efficient use of IP addresses, and enhanced security.
• 😀 CDR (Classless Interdomain Routing) eliminates the reliance on IP classes, using a prefix to determine subnet masks, providing more flexibility in IP address allocation.
• 😀 In CDR, subnet masks are determined by the prefix length (e.g., a /25 prefix means 25 bits of 1s for the subnet mask).
• 😀 The prefix in CDR allows for a more granular allocation of IPs compared to classful addressing, enabling networks to be broken down efficiently.
• 😀 The importance of calculating the network address (ENA) and broadcast address (BEA) for each subnet is highlighted, as well as understanding how to determine usable host addresses (RHA).
• 😀 The tutorial emphasizes that practice and understanding of CDR concepts, such as prefix length, subnet masks, and calculating ENA, BEA, and RHA, are essential for efficient network configuration.

Q & A

What is Classless Interdomain Routing (CDR)?

Classless Interdomain Routing (CDR) is a method for allocating IP addresses and routing Internet Protocol packets that doesn't rely on the traditional classful IP addressing system (Class A, B, C). Instead, CDR uses a prefix notation to indicate how many bits are allocated to the network part of the address.

How does CDR differ from classful addressing?

In classful addressing, IP addresses are divided into classes (A, B, C), each with predefined subnet masks. CDR, on the other hand, uses a prefix notation (e.g., /24) to define the number of bits for the network portion of the address, allowing for more flexible and efficient address allocation.

What is the role of the prefix in CDR?

The prefix in CDR (e.g., /24, /25) specifies the number of bits used for the network portion of an IP address. This allows network administrators to create subnets of varying sizes, offering more efficient use of IP address space compared to classful addressing.

Why is subnetting important in network management?

Subnetting is important because it divides a larger network into smaller, more manageable subnets. This reduces broadcast traffic, improves security, and makes it easier for network administrators to manage and allocate IP addresses more efficiently.

How do you calculate the total number of IP addresses in a subnet?

The total number of IP addresses in a subnet is calculated using the formula 2^n, where 'n' is the number of bits available for the host portion. For example, a subnet with 8 bits for hosts (like a /24 prefix) would have 256 IP addresses.

What is the difference between network address, broadcast address, and host range?

The network address is the first IP address in a subnet, and it represents the subnet itself. The broadcast address is the last IP address in the subnet, used for broadcasting messages to all devices within the subnet. The host range consists of the IP addresses that can be assigned to devices, excluding the network and broadcast addresses.

What is a subnet mask, and how is it determined in CDR?

A subnet mask defines the network and host portions of an IP address. In CDR, the subnet mask is determined by the prefix. For example, a prefix of /25 corresponds to a subnet mask of 255.255.255.128.

How do you calculate the total number of hosts in a subnet?

The total number of hosts in a subnet is calculated by subtracting 2 from the total number of IP addresses (2^n - 2). The subtraction accounts for the network and broadcast addresses, which cannot be assigned to hosts.

What are some of the benefits of using CDR over classful addressing?

The benefits of CDR over classful addressing include more efficient use of IP address space, greater flexibility in subnet size, and reduced waste of IP addresses. CDR allows for better scalability and network management in modern networks.

Can you explain the formula used to calculate the number of hosts in a subnet?

The formula for calculating the number of hosts is 2^n - 2, where 'n' is the number of bits allocated for hosts. The '2' is subtracted because the network address and broadcast address cannot be used by hosts.