The /24 subnet, explained
Everything about a /24 CIDR block — mask, address count, usable hosts and where a /24 fits in real network plans.
| Prefix length | /24 — 24 network bits, 8 host bits |
| Subnet mask | 255.255.255.0 |
| Wildcard (ACL) mask | 0.0.0.255 |
| Binary mask | 11111111.11111111.11111111.00000000 |
| Total addresses | 2^8 = 256 |
| Usable hosts | 254 (total − network − broadcast) |
| A /16 holds | 256 × /24 subnets |
| Example block | 192.168.1.0/24 |
Notes
A /24 prefix means the first 24 bits of the 32-bit IPv4 address identify the network and the remaining 8 bits identify hosts — giving 2^8 = 256 addresses. The first address (network) and the last (broadcast) are not assignable in a standard subnet.
Cloud sizing: a /24 is valid as an AWS VPC (allowed range /16–/28). AWS reserves 5 addresses per subnet, so a /24 subnet gives 251 assignable IPs there; GCP reserves 4 (252 assignable).
Adjacent sizes: /8 · /9 · /10 · /11 · /12 · /13 · /14 · /15 · /16 · /17 · /18 · /19 · /20 · /21 · /22 · /23 · /25 · /26 · /27 · /28 · /29 · /30 · /31 · /32
Frequently asked questions
How many IP addresses are in a /24?
256 total addresses, of which 254 are usable hosts (network and broadcast addresses are reserved).
What is the subnet mask for /24?
255.255.255.0 (wildcard mask 0.0.0.255).
What does /24 mean in an IP address?
The /24 suffix is CIDR notation: the first 24 bits are the network part, the last 8 bits are the host part.