/24 Subnet: Mask 255.255.255.0

A /24 is the subnet everyone knows: the first three octets name the network and the last octet (0–255) is for hosts. Home routers, most office VLANs and most tutorials use it, and it is also the smallest block generally accepted in the global BGP table.

/24 at a glance

Subnet mask
255.255.255.0
Wildcard mask
0.0.0.255
Usable hosts
254
Total addresses
256 (28)
Block size (third octet)
1
Network / host bits
24 / 8
Mask in hex
0xFFFFFF00

Mask in binary: 11111111.11111111.11111111.00000000

Network bits Host bits

Try it: which /24 is an address in?

Network address
192.168.1.0/24
First usable host
192.168.1.1
Last usable host
192.168.1.254
Broadcast address
192.168.1.255
Next /24 starts at
192.168.2.0
Open this in the full subnet calculator (binary view, exports, cloud reserved IPs) →

How many /24 networks fit

How /24 relates to /8, /16 and /24 blocks
Parent block Relationship
/8 65,536 × /24 fit inside one /8
/16 256 × /24 fit inside one /16
/24 Same size: a /24 is exactly one /24

256 × /24 make a /16. Inside a /24 you can fit 2 × /25, 4 × /26, 8 × /27, 16 × /28 or 64 × /30.

Worked example: 192.168.1.137/24

Your laptop has 192.168.1.137 with mask 255.255.255.0. Let's confirm the network, broadcast and usable range — the numbers you need to set a static IP without clashing.

  1. /24 is 3 full octets of network bits (mask 255.255.255.0), so the boundary falls exactly between octets. No block-size maths is needed.
  2. Keep the first 3 octets of 192.168.1.137 and set the rest to 0: network = 192.168.1.0.
  3. Set the rest to 255 instead: broadcast = 192.168.1.255.
  4. Usable hosts run from 192.168.1.1 to 192.168.1.254: 28 − 2 = 254.

Same thing in binary (network bits | host bits):

Address  11000000.10101000.00000001|10001001
Mask     11111111.11111111.11111111|00000000
Network  11000000.10101000.00000001|00000000

Where /24 is used in real networks

  • Home and small office LANs

    Nearly every home router hands out a /24, usually 192.168.1.0/24 or 192.168.0.0/24. The router takes .1 and DHCP hands out a pool such as .100 to .200.

  • One VLAN per /24

    In offices, a /24 per VLAN keeps things easy to read: 10.10.20.0/24 is VLAN 20, 10.10.30.0/24 is VLAN 30. Matching the third octet to the VLAN ID saves a lot of time during outages.

  • Smallest routable block on the Internet

    Most networks filter BGP announcements longer than /24, so a /24 is the smallest IPv4 block you can usefully announce, for example for your own provider-independent space.

Common /24 mistakes

  • Assuming every network is a /24. If a device has mask 255.255.254.0 or 255.255.255.128, the network and broadcast are different. Always check the mask before picking an address.
  • Setting a static IP inside the DHCP pool. The router may later lease the same address to another device and you get an IP conflict. Reserve a range (e.g. .2 to .49) for static devices.
  • Planning a VPN between two sites that both use 192.168.1.0/24. Traffic for the other side never leaves the local LAN. Re-number one site first — see the overlap checker.

/24 FAQ

How many usable IP addresses are in a /24?

254. There are 256 addresses (.0 to .255); .0 is the network address and .255 is the broadcast.

What is the wildcard mask for /24?

0.0.0.255. In a Cisco ACL: permit ip 192.168.1.0 0.0.0.255 any.

Is 255.255.255.0 the same as /24?

Yes. 255.255.255.0 is 24 one-bits followed by 8 zero-bits, which is written /24 in CIDR notation.

How many /24s are in a /16?

256. The third octet can take 256 values (0 to 255), and each one is a separate /24.

Related tools

Subnet Calculator Full /24 breakdown with binary and exports Wildcard Mask Calculator ACL and OSPF wildcard for /24 and every other prefix CIDR Calculator Split 192.168.1.0/24 into smaller blocks VLSM Calculator Mix /24 with other sizes in one plan Subnet Mask Calculator Convert mask ↔ prefix ↔ host count Subnetting Practice Drill questions like this one, with visual answers

Well-known /24 networks: 10.0.0.0/24, 192.168.0.0/24, 192.168.1.0/24