17. Subnetting 3 - Prefiks Yang Paling Efektif

Summary

In this video, the presenter explains how to determine the most effective subnet for a network with 15 devices. After going over basic exponent calculations for subnetting, the presenter concludes that a 32 IP address range is the best fit for 15 PCs, as 16 addresses are insufficient due to network and broadcast addresses being reserved. The chosen prefix is /27, and the IP address format is demonstrated with a sample like 10.10.10/27. The video wraps up by confirming the optimal subnet and the chosen IP address for the network.

Takeaways

• 😀 Subnetting calculations are essential to determine the most effective prefix for a network.
• 😀 The goal is to determine the most efficient prefix based on the number of devices (15 PCs in this case).
• 😀 Exponentiation is used to calculate the available IP address range (e.g., 2^4 = 16, 2^5 = 32, etc.).
• 😀 While 16 IP addresses might seem sufficient, 2 are reserved for network and broadcast addresses, leaving only 14 usable IPs.
• 😀 Since 15 PCs cannot fit within 16 usable IPs, a larger network size of 32 IPs is needed.
• 😀 The appropriate prefix for 32 IP addresses is /27 (i.e., 32-5 = 27).
• 😀 The prefix /27 corresponds to a subnet mask of 255.255.255.224.
• 😀 For the network address, the prefix /27 must be applied to a suitable base IP address.
• 😀 The base IP address can be 10.10.10.0, with the prefix /27 added for subnetting.
• 😀 The network and broadcast addresses should always be excluded from usable IPs, making them unavailable for host allocation.

Q & A

What is the main objective of the video?

The main objective of the video is to provide an example of subnetting, specifically focusing on how to calculate the most effective prefix for a network that requires IP addressing for 15 devices in a computer room.

Why is the most effective prefix for 15 devices not 16?

The most effective prefix for 15 devices is not 16 because 16 addresses would need to reserve two addresses for the network and broadcast, leaving only 14 usable IPs, which is not enough for 15 devices. Therefore, a larger prefix of 32 addresses is used.

What is the significance of the number 32 in the subnetting calculation?

The number 32 represents the total number of bits in an IPv4 address. In subnetting, this is used to calculate the number of IP addresses available, where the network portion of the address is subtracted from the total 32 bits.

How do the exponents of 2 help in determining the number of available addresses?

The exponents of 2 represent the number of possible IP addresses for a given subnet. For example, 2^4 gives 16 addresses, and 2^5 gives 32 addresses. These are used to find the closest subnet that can accommodate the required number of devices.

What does the subnet prefix of /27 mean in this case?

A /27 subnet means there are 32 total IP addresses available in the subnet, with 5 bits used for the host portion. This is calculated as 32 - 5 = 27, making it the most efficient prefix for 15 devices.

Why are two addresses in the subnet always reserved for network and broadcast?

In any subnet, the first address is reserved for the network identifier, and the last address is reserved for the broadcast address. These cannot be assigned to devices, so the total usable IPs are always reduced by 2.

What does the phrase 'the first three numbers will remain' refer to?

This refers to the IP address format, where the first three octets (numbers) remain fixed, and only the last octet can be modified to assign different IPs within the subnet. In this case, '10.10.10' remains constant while the last segment is adjusted.

How does the selection of the IP address range fit into the subnetting process?

After determining the most effective prefix, the IP address range is selected. In this case, the example uses the range '10.10.10.0/27'. The prefix /27 is chosen based on the subnetting calculations, and the first three segments '10.10.10' stay the same.

What is the role of the network and broadcast addresses in subnetting?

The network address identifies the subnet itself and cannot be assigned to any device. The broadcast address is used to send data to all devices on the subnet simultaneously. Both of these addresses are reserved, reducing the total number of usable IP addresses in the subnet.

Why was 32 chosen as the closest number of IP addresses for 15 devices?

32 addresses were chosen because 16 addresses were insufficient after reserving 2 for the network and broadcast addresses. The next available option, 32, provides enough addresses for 15 devices, ensuring that there are sufficient usable IP addresses.