Mengenal Teknik CIDR dan VLSM

Summary

This script explains key concepts in networking, focusing on IP addressing, classful and classless addressing, subnetting, and Variable-Length Subnet Masking (VLSM). It covers the differences between classful addressing (such as class A, B, C) and classless addressing, detailing how subnetting works for efficient IP address allocation. The script also touches on network division using CIDR notation, calculating available hosts, and optimal allocation for networks with varying device requirements, using examples like the IP address '192.168.1.1' and different subnet masks.

Takeaways

• 😀 Classful IP addressing uses predefined subnet masks (e.g., Class A, B, C), with fixed sizes that limit flexibility.
• 😀 Classless IP addressing (CIDR) allows more flexibility by using custom subnet masks, not relying on predefined classes.
• 😀 In classful addressing, Class A, B, and C are the main categories, each with a default subnet mask (Class A: 8-bit, Class B: 16-bit, Class C: 24-bit).
• 😀 Supernetting is a technique used in classful addressing to aggregate networks and reduce the number of entries in a routing table.
• 😀 Subnetting is used in classful addressing to divide a network into smaller sub-networks for efficient IP address allocation.
• 😀 The process of calculating network and broadcast IDs involves converting IP addresses and subnet masks into binary and applying logical operations.
• 😀 VLSM (Variable Length Subnet Masking) is introduced as a way to optimize IP address usage by assigning different subnet masks to different subnets, thus minimizing wastage.
• 😀 The example of a university with various departments (e.g., laptops, academy, and finance) illustrates how to allocate subnet masks based on the number of hosts required in each subnet.
• 😀 In classless addressing, subnet masks can be customized to fit the network's needs, for example, 192.168.1.0/26 allows four subnets.
• 😀 A classless network can have multiple subnetworks within a single classful address range, and subnet size is determined by the network's specific needs, as shown with CIDR notation.
• 😀 Calculations for host and subnet size are based on the number of bits used in the subnet mask. For example, with a /26 subnet mask, 64 total IP addresses are possible, with 62 usable addresses after excluding network and broadcast addresses.

Q & A

What is the main topic discussed in the script?

The script mainly discusses IPv4 addressing concepts, including classful and classless addressing, CIDR, subnetting, supernetting, and Variable Length Subnet Masking (VLSM).

What is meant by classful IP addressing?

Classful IP addressing is an older IPv4 addressing method that divides IP addresses into fixed classes (A, B, C, D, and E) with default subnet masks, such as /8 for Class A, /16 for Class B, and /24 for Class C.

Why is classful addressing considered inefficient?

Classful addressing is inefficient because it uses fixed subnet sizes, which often leads to wasted IP addresses when the number of hosts does not match the default class size.

What is classless IP addressing (CIDR)?

Classless IP addressing, also known as CIDR (Classless Inter-Domain Routing), allows flexible subnet masks that are not tied to IP classes, enabling more efficient allocation of IP addresses.

What does the prefix notation like /24 or /26 represent?

The prefix notation indicates the number of bits set to 1 in the subnet mask. For example, /24 means 24 bits are used for the network portion, leaving 8 bits for host addresses.

How is the number of hosts in a subnet calculated?

The number of usable hosts is calculated using the formula 2^n − 2, where n is the number of host bits. The subtraction of 2 accounts for the network ID and broadcast address.

What is subnetting and why is it used?

Subnetting is the process of dividing a larger network into smaller subnetworks to improve network organization, performance, and efficient use of IP addresses.

What is supernetting as mentioned in the script?

Supernetting is the opposite of subnetting; it combines multiple smaller networks into a larger one and is often used in routing to reduce routing table size.

What is VLSM (Variable Length Subnet Mask)?

VLSM is a subnetting technique that allows different subnet masks for different subnets within the same network, enabling more efficient IP address usage.

Why does VLSM start allocating IPs from the largest host requirement?

VLSM starts with the largest host requirement to ensure that large subnets receive sufficient IP addresses first, preventing address space fragmentation.

In the example given, why was a /26 subnet chosen for 50 hosts?

A /26 subnet provides 64 total addresses and 62 usable hosts, which is sufficient to accommodate 50 hosts without wasting too many IP addresses.

What are network ID and broadcast ID, and why can’t they be used by hosts?

The network ID identifies the subnet itself, and the broadcast ID is used to send data to all hosts in the subnet. They are reserved addresses and cannot be assigned to individual hosts.