Enter an IPv4 address with a prefix (e.g. 192.168.1.10/24) or pick the subnet mask from the list.
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Binary view
Split this network further
| # | Network | First host | Last host | Broadcast |
|---|
The prefix (the number after the slash) says how many bits of the address belong to the network. The rest identifies the hosts inside it. A /24 has 24 network bits and 8 host bits, so 256 addresses – 254 of them usable, because the first (network) and the last (broadcast) are reserved. The smaller the prefix, the larger the network.
Frequently asked questions about subnetting
What does the number after the slash mean, for example /24?
That number is the CIDR prefix and states how many of the 32 bits of an IPv4 address belong to the network. With /24 it is the first 24 bits, leaving 8 bits for the hosts inside the network. It corresponds to the subnet mask 255.255.255.0.
How many hosts fit into a /24 network?
A /24 network covers 256 addresses, 254 of which are usable for hosts. The first address is the network address and the last one is the broadcast address – neither can be assigned to a device.
Why are only 254 of 256 addresses usable?
Two addresses in every network are reserved: the network address, which identifies the network itself, and the broadcast address, which reaches every device at once. The formula is therefore 2host bits − 2.
What is the difference between a subnet mask and a wildcard mask?
The wildcard mask is the bitwise inverse of the subnet mask. The subnet mask 255.255.255.0 pairs with the wildcard 0.0.0.255. Wildcard masks are mainly used in Cisco access control lists (ACLs) and in OSPF configurations.
Which IP ranges are private?
RFC 1918 reserves three ranges for private networks: 10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16. Addresses from these ranges are not routed on the internet and are meant for home and company networks behind a router.
What is a /31 network used for?
A /31 network holds just two addresses and is used for point-to-point links between two routers, as defined in RFC 3021. There is no network or broadcast address, so both addresses are usable as endpoints.
How do I find out my own subnet mask?
On Windows the ipconfig command in the command prompt shows the IPv4 address and the subnet mask of the device. On Linux and macOS, ip addr or ifconfig give you the same details.
To watch network connections live and block individual IPs or ports, try Alpha10 NetGuard. For logging reachability and packet loss over time, use the Ping Logger.