IP address classes

Class1st Octet Decimal Range1st Octet High Order Bits

Network/Host ID
(N=Network, H=Host)

Default Subnet MaskNumber of NetworksHosts per Network
(Usable Addresses)
A 1 – 126* 0 N.H.H.H 255.0.0.0 126 (27 – 2) 16,777,214 (224 – 2)
B 128 – 191 10 N.N.H.H 255.255.0.0 16,382 (214 – 2) 65,534 (216 – 2)
C 192 – 223 110 N.N.N.H 255.255.255.0 2,097,150 (221 – 2) 254 (28 – 2)
D 224 – 239 1110 Reserved for Multicasting
E 240 – 254 1111 Experimental; used for research

Note: Class A addresses 127.0.0.0 to 127.255.255.255 cannot be used and is reserved for loopback and diagnostic functions.

 

Private IP Addresses

ClassPrivate NetworksSubnet MaskAddress Range
A 10.0.0.0 255.0.0.0 10.0.0.0 - 10.255.255.255
B 172.16.0.0 - 172.31.0.0 255.240.0.0 172.16.0.0 - 172.31.255.255
C 192.168.0.0 255.255.0.0 192.168.0.0 - 192.168.255.255


Subnet Mask Cheat Sheet

 AddressesHostsNetmaskAmount of a Class C
/30 4 2 255.255.255.252 1/64
/29 8 6 255.255.255.248 1/32
/28 16 14 255.255.255.240 1/16
/27 32 30 255.255.255.224 1/8
/26 64 62 255.255.255.192 1/4
/25 128 126 255.255.255.128 1/2
/24 256 254 255.255.255.0 1
/23 512 510 255.255.254.0 2
/22 1024 1022 255.255.252.0 4
/21 2048 2046 255.255.248.0 8
/20 4096 4094 255.255.240.0 16
/19 8192 8190 255.255.224.0 32
/18 16384 16382 255.255.192.0 64
/17 32768 32766 255.255.128.0 128
/16 65536 65534 255.255.0.0 256


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