The Tool Desk
Outbyte Driver Updater FREEScan for outdated or missing drivers - takes under a minuteDriver Scan →Outbyte PC Repair FREEClear out junk files and repair common Windows errorsFree Scan →A Class C network is a legacy classful IPv4 network with a 21-bit network number and 8 bits for local addresses. Its conventional mask is 255.255.255.0, or /24. That block contains 256 address values, of which 254 are ordinarily assignable to hosts. Today, however, IPv4 networks use explicitly configured CIDR prefixes; an address does not determine its network size by class.
What “Class C” means
IPv4 addresses are 32 bits long. In the historical classful system, a Class C address began with the binary bits 110. The class implied that the first 24 bits identified the network and the last 8 bits were available for local addresses.
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In dotted-decimal notation, that implied mask is 255.255.255.0: the first three octets correspond to network bits, and the final octet corresponds to host bits. For example, RFC 4632 gives 192.168.99.0/24 as a legacy Class C example. The /24 says that 24 of the 32 address bits form the prefix.
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With 8 host bits, a /24 contains 28 = 256 total address values. Under 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, leaving 254 ordinary host addresses.
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That 254 figure is the familiar answer for a conventional /24, not a universal rule for every prefix or point-to-point configuration. RFC 4632 describes the historical Class C network as having 254 end systems.
Is Class C the same as /24 today?
Historically, Class C implied a /24. In modern CIDR addressing, the prefix length is written explicitly, so the configured prefix—not an address’s first octet—determines the block size. RFC 4632 explains that explicit classless prefixes allow address blocks to match actual need.
For instance, 192.168.99.0/26 is a /26 block even though the address falls within a range historically associated with Class C. A /26 has 26 prefix bits and 6 remaining address bits, so its block contains 64 address values; the historical class does not turn it into a /24.
Why the term is considered legacy
Class A, B, and C once described fixed network sizes. CIDR replaced those implied boundaries with explicit prefix lengths, allowing blocks of different sizes to be specified and aggregated. As a result, “Class C” remains useful when reading older networking material, but for a current network description, use the actual CIDR notation and mask.
RFC 997, published in 1986, recorded 2,097,152 possible Class C networks in the classful system. This is a historical count, not a current IPv4 allocation statistic. RFC 4632, an IETF Best Current Practice published in August 2006, describes the move toward classless prefixes and flexible block sizing.
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References
- RFC 4632, Classless Inter-domain Routing (CIDR): The Internet Address Assignment and Aggregation Plan, IETF / RFC Editor, August 2006.
- RFC 997, Internet Numbers, IETF / RFC Editor, January 1986.
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