Maximizing the Utilization of IPv4 Addresses with Subnet Mask 255.255.255.224

When planning the allocation of IPv4 addresses in a local network, understanding how to effectively use subnet masks is crucial for maximizing the number of available IP addresses. In this article, we will explore how to determine the maximum number of IP addresses that can be assigned with a local subnet mask of 255.255.255.224. We'll break down the formula, provide practical examples, and discuss the significance of network and broadcast addresses.

Understanding Subnet Masks

Subnet masks are used to divide an IP address into network and host components. A subnet mask of 255.255.255.224, when represented in CIDR notation, is /27. This means that the first 27 bits are used for the network part, leaving 5 bits for the host part. This can be represented as:

255.255.255.224  11111111.11111111.11111111.11100000

Calculating Usable IP Addresses

The formula to calculate the number of usable IP addresses in a subnet is:

Usable IPs 2n - 2

Where n is the number of bits available for hosts. In the case of /27, the number of bits available for hosts is 5. Therefore, the number of usable IP addresses can be calculated as follows:

25  3232 - 2  30

We subtract 2 from the total to account for the network address and the broadcast address, which cannot be assigned to hosts. Hence, with a subnet mask of 255.255.255.224, the maximum number of assignable IP addresses is 30.

Practical Example with a Class C Address

Let's apply this concept with a Class C address, which has a default mask of 255.255.255.0. By using a subnet mask of 255.255.255.224, or /27, we can break down the IP addresses as follows:

The first 27 bits are used for the network ID (NET-ID). The last 5 bits are used for the host ID (HOST-ID).

Given that there are 32 possible combinations of the last 5 bits, the total number of IP addresses is 32. However, the network address and broadcast address must be excluded, leaving us with:

32 - 3  29

Thus, there are 29 IP addresses that can be assigned to PCs on the local network.

Conclusion

Understanding how to effectively use subnet masks is essential for efficient IP address management in local networks. By utilizing a subnet mask of 255.255.255.224, you can maximize the number of usable IP addresses while ensuring proper network segmentation. Remember to account for the network address, broadcast address, and any reserved addresses when assigning IP addresses to devices on the network.