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What Does /24 Mean After an IPv4 Address?

The /24 is a CIDR prefix length: the first 24 of an IPv4 address’s 32 bits identify the network prefix, leaving 8 bits for addresses within that block. A /24 therefore contains 256 total addresses.

Find the block containing 192.0.2.137/26

prefix:     /26
block size:  64
ranges:      0–63, 64–127, 128–191, 192–255
result:      192.0.2.128/26

The address is in the 128–191 block. In traditional subnetting, .128 is the network address and .191 the directed broadcast; platform reservations may further reduce assignable addresses.

Prefix length defines a bit boundary

IPv4 contains 32 bits. Writing 192.0.2.0/24 is equivalent to the subnet mask 255.255.255.0 because the mask has 24 leading one bits. The remaining eight bits can represent values from 0 through 255. The network that contains a particular address is found by applying the mask, not by guessing from decimal punctuation.

A shorter prefix represents a larger block because more bits remain variable. A /16 contains 65,536 addresses; a /30 contains four; a /32 identifies one address. Adjacent blocks start only on valid binary boundaries, so 192.0.2.64/26 is aligned while 192.0.2.70/26 describes an address inside that same aligned block rather than a new block beginning at 70.

Total addresses are not always usable host addresses

In a traditional IPv4 subnet, the all-zero host portion names the network and the all-one host portion is the directed broadcast address, leaving 254 conventional host addresses in a /24. Context matters: /31 has special point-to-point semantics, /32 is a host route, cloud providers reserve additional addresses, and a routed prefix can be used differently from a LAN. Always apply the platform’s rules after doing the CIDR math.

Translate prefix length into address boundaries

PrefixMaskTotal addressesCommon interpretation
/16255.255.0.065,536Large block
/24255.255.255.0256Common LAN-sized block
/30255.255.255.2524Small traditional subnet
/32255.255.255.2551Single address or host route

Subnet shortcuts that lose important context

“Class C” is historical language and does not replace an explicit CIDR prefix.

Private versus public addressing is determined by registered ranges, not by the prefix length alone.

A subnet mask configures an interface’s on-link decision; it does not automatically create routing, firewall, or DHCP configuration.

Work out a /24 without guessing

  • Identify the address family; IPv6 uses the same prefix notation with 128 total bits.
  • Calculate total addresses as 2 raised to the number of remaining address bits.
  • Find the aligned network boundary before listing a range.
  • Check the router, operating system, or cloud provider’s reservation rules before assigning hosts.

Questions about /24 networks

Is every /24 a private network?

No. /24 describes size only. Whether addresses are private, documentation-only, public, or special-purpose depends on the actual prefix.

Does a /24 always have 254 usable hosts?

It contains 256 addresses. 254 is a conventional LAN calculation, but provider reservations and special subnet semantics can change assignability.

Put the concept into practice

Try the Subnet Calculator with harmless sample data. Then connect the idea to A, AAAA, and CNAME records.

Definitions and standards behind the answer