iTechGuides is reader-supported. When you buy through links on our site, we may earn an affiliate commission. As an Amazon Associate I earn from qualifying purchases. Learn more
A legacy Class C network is an IPv4 network with a 24-bit network prefix and 8 host bits. Its conventional subnet mask is 255.255.255.0, or /24. That block contains 256 addresses, of which 254 are ordinarily assignable to hosts. Today, however, networks use explicit CIDR prefixes; an IPv4 address does not determine its subnet mask by class.
What “Class C” means
IPv4 addresses are 32 bits long. Under the historical classful system, Class C addresses began with the binary pattern 110. The class implied a 21-bit network number after that leading pattern, followed by 8 bits for local addresses. In practical subnet notation, the familiar Class C network is represented as a /24.
![Computer Networking Bible: [3 in 1] The Complete Crash Course to Effectively Design, Implement and Manage Networks. Including Sections on Security, Performance and Scalability](https://m.media-amazon.com/images/I/41H4YJnxKgL._SL160_.jpg)
For example, 192.168.99.0/24 is an example of a legacy Class C-sized network cited in RFC 4632. The slash notation says that the first 24 bits identify the network prefix and the remaining 8 bits vary within the block.
What is the Class C subnet mask?
The conventional Class C mask is 255.255.255.0. In binary, its first 24 bits are ones and its final 8 bits are zeros, matching the /24 prefix length.
#1 Best Overall
How many addresses and hosts does a /24 have?
Eight host bits provide 28 = 256 total address values. In conventional IPv4 subnetting, the all-zero host value identifies the network address and the all-one host value is the directed broadcast address. Those two values are not assigned to ordinary hosts, so the familiar usable-host count for a standard /24 is 254.
This 254 figure is the conventional answer for an ordinary IPv4 /24 subnet, not a universal rule for every prefix length or point-to-point configuration. RFC 4632 describes 254 end systems in its historical discussion of Class C.
Is Class C the same as /24?
In the old classful system, Class C implied the conventional /24 boundary. In modern CIDR, the prefix length is written explicitly and can be chosen to fit the network. An address in a historically Class C range does not automatically have a /24 mask: for instance, 192.168.99.0/26 is a /26 block because the stated prefix is 26 bits.
Quick wins for a faster PC:
Clear out junk files and repair common Windows errorsFree Scan →Fix the driver behind crashes, sound loss and screen glitchesFind Drivers →Repair Windows errors before they cause bigger problemsFix Now →RFC 4632 explains that explicit CIDR prefixes allow address blocks to be matched more flexibly to actual need. The practical distinction is that classful addressing implied a boundary from the address class, while CIDR specifies the boundary directly.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Why the term is considered legacy
Class A, B, and C were part of an earlier classful addressing model. RFC 997, published in 1986, records 2,097,152 possible Class C networks—a historical classful count, not a current allocation statistic. Modern network planning and routing use CIDR prefixes rather than choosing a network size from its class. For current subnet questions, read the configured slash length or subnet mask instead of inferring one from the first octet.
Quick Recap
Best Value
Rank #4
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
