breakitdown

What does /24 mean?

Answer

A /24 keeps the first three numbers fixed and lets the last one vary: 256 addresses, 254 usable hosts. The netmask is 255.255.255.0. In 192.168.1.0/24, the network is 192.168.1.0, the broadcast is 192.168.1.255, and hosts are 192.168.1.1 to 192.168.1.254.

Worked example: 192.168.1.0/24. Type any block to compare.

Try

192.168.1.0/24 is 256 addresses: 192.168.1.0 to 192.168.1.255. 254 usable for hosts (the first is the network address, the last is broadcast).

1921100000016810101000100000001000000000
24 network bits 8 host bits
Network
192.168.1.0
First usable
192.168.1.1
Last usable
192.168.1.254
Broadcast
192.168.1.255
Addresses
256
Usable hosts
254
Netmask
255.255.255.0
Wildcard (ACL) mask
0.0.0.255
Historic class
C
Range type
Private network · not routed on the internet

Special-purpose range

Private network 192.168.0.0/16 RFC 1918
The private range most home routers use (192.168.0.x, 192.168.1.x).

Split it into subnets

or

4 subnets.

SubnetUsable rangeHostsBroadcast
192.168.1.0/26192.168.1.1 – 192.168.1.6262192.168.1.63
192.168.1.64/26192.168.1.65 – 192.168.1.12662192.168.1.127
192.168.1.128/26192.168.1.129 – 192.168.1.19062192.168.1.191
192.168.1.192/26192.168.1.193 – 192.168.1.25462192.168.1.255

Is this IP in the range?

Range to CIDR blocks

What to know

/24 is the default LAN on most home routers (192.168.0.0/24 or 192.168.1.0/24, with the router at .1) and the most common subnet size in offices and cloud VPCs. In AWS, a /24 subnet gives 251 usable addresses after the 5 reserved ones; Google Cloud reserves 4, leaving 252.

On the public internet, /24 is the longest (most specific) IPv4 prefix most networks accept in BGP, so it is also the smallest block an organization can usually announce on its own.

Gotchas

Related explainers

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