IP Address & Subnet Reference
A complete, calculated IPv4 reference: every subnet mask from /8 to /30, the common private /24 blocks with their usable ranges, and the special addresses every network engineer must know. All values are computed, not estimated.
Worked prefix guides
Use these detailed examples to practise small LANs, VLAN sizing and aligned route summaries:
Subnet masks by prefix
Every CIDR prefix, its dotted-decimal mask, host count and wildcard:
/1 /2 /3 /4 /5 /6 /7 /8 /9 /10 /11 /12 /13 /14 /15 /16 /17 /18 /19 /20 /21 /22 /23 /24 /25 /26 /27 /28 /29 /30 /31 /32
See the printable subnet mask cheat sheet.
Special-purpose addresses
127.0.0.1 0.0.0.0 255.255.255.255 169.254.0.0/16 10.0.0.0/8 172.16.0.0/12 192.168.0.0/16
Calculate any subnet
Need a custom subnet? Our free subnet calculator computes network, broadcast, mask and host range for any address and prefix instantly.
Frequently asked questions
What is a subnet mask?
A subnet mask marks which part of an IP address is the network and which is the host. For example /24 (255.255.255.0) uses 24 network bits and 8 host bits, giving 254 usable hosts.
How do I find the usable range of a subnet?
Take the network address plus 1 as the first host and the broadcast address minus 1 as the last host. Our per-subnet pages and calculator show this for any block.
What are the private IP ranges?
10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16 (RFC 1918). They are used inside private networks and are not routable on the public internet.
Related
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