Network: IPv4 subnetting reference

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CIDRHost bitsNetmaskAddresses in subnetClassful nameTypical usage
/824255.0.0.016777216 = 224Class A (see this list)Largest block allocation made by IANA
/923255.128.0.08388608 = 223
/1022255.192.0.04194304 = 222
/1121255.224.0.02097152 = 221
/1220255.240.0.01048576 = 220
/1319255.248.0.0524288 = 219
/1418255.252.0.0262144 = 218
/1517255.254.0.0131072 = 217
/1616255.255.0.065536 = 216Class B
/1715255.255.128.032768 = 215ISP / large business
/1814255.255.192.016384 = 214ISP / large business
/1913255.255.224.08192 = 213ISP / large business
/2012255.255.240.04096 = 212Small ISP / large business
/2111255.255.248.02048 = 211Small ISP / large business
/2210255.255.252.01024 = 210
/239255.255.254.0512 = 29
/248255.255.255.0256 = 28Class CLarge LAN
/257255.255.255.128128 = 27Large LAN
/266255.255.255.19264 = 26Small LAN
/275255.255.255.22432 = 25Small LAN
/284255.255.255.24016 = 24Small LAN
/293255.255.255.2488 = 23Smallest multi-host network
/302255.255.255.2524 = 22"Glue network" (point to point links)
/311255.255.255.2542 = 21Rarely used, point to point links (RFC 3021)
/320255.255.255.2551 = 20Host route

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