This article provides a step-by-step guide to allocating IPv4 addresses within a small business network using a Class C subnet. It covers key concepts like subnet masks, networks, and broadcast addresses. It also provides an example of an IP addressing scheme for devices like servers, printers, and VoIP phones.
Regardless of the size of a network, proper IP address allocation is crucial for the efficiency and security of a network. This article examines a scenario where a network administrator needs to assign IPv4 addresses within a small Class C network (192.168.1.0/24 with a subnet mask of 255.255.255.0, providing 254 usable addresses). The network comprises 100 nodes, including four servers (a domain controller, a replica, a data server, and a web server), a network printer, and a VoIP phone system.
Overview of the network
It is important before assigning IP addresses to devices to understand the purpose of each device and a plan for IP address allocation. This section analyses the provided Class C network scheme.
Subnet Mask: 255.255.255.0 (or /24) — This is the classful subnet mask for a Class C network.
Table 1
IP Address class
Note: From “Lesson 5: IPv4 and IPv6 addresses. CompTIA Network+ Pearson N10–007 (Course & Labs) ” by uCertify (2019).
Host IP Addresses
Total Possible IP Addresses:
The /24 subnet mask represents the first 24 bits of the IP address that are used to identify the network, the last 8 bits (32 total bits — 24 network bits = 8 host bits) are used to identify the host IP addresses.
With 8 bits, you can have 28 (2 to the power of 8) or 256 IP address combinations.
Therefore, there are 256 possible IP addresses within the 192.168.1.0/24 network.
Reserved Addresses (Network and Broadcast):
Network Address: the first possible address is reserved for the network address. It has all the bits set to 0. For this example, it is 192.168.1.0.
Broadcast Address: The last possible address is reserved for the directed broadcast address. This address has all bits set to 1. For this example, it is 192.168.1.255.
Host Usable IP Addresses:
Since the network address and the broadcast address are reserved, they cannot be assigned to hosts.
Therefore, the number of usable host IP addresses is 256–2 = 254.
To calculate the total possible host IP addresses the following formula is used:
2ʰ-2
where h is the number of host bits in a subnet mask, for example, is:
2⁸–2 = 256–2 = 254
See the table below.
Table 3
Usable Host IP Addresses
on Medium - Level UP Coding on January 5, 2025
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