Private IPv4 address spaces

IANA-reserved private IPv4 network ranges
Start End No. of addresses
24-bit block (/8 prefix, 1 × Class A) 10.0.0.0 10.255.255.255 16777216
20-bit block (/12 prefix, 16 × Class B) 172.16.0.0 172.31.255.255 1048576
16-bit block (/16 prefix, 256 × Class C) 192.168.0.0 192.168.255.255 65536

 

For “Classful” networks, the network and host portions are as follows:
(“n” represents the network portion, “x” represents the host portion)

When the first number is 0 to 126 – nnn.xxx.xxx.xxx (ex. 10.xxx.xxx.xxx)
These are known as “Class A” networks.

When the first number is 128 to 191 – nnn.nnn.xxx.xxx (ex. 172.16.xxx.xxx)
These are known as “Class B” networks.

When the first number is 192 to 223 – nnn.nnn.nnn.xxx (ex. 192.168.1.xxx)
These are known as “Class C” networks.

When the first number is 224 to 239 – The address is used for multi-casting.

When the first number is 240 to 255 – The address is “experimental”.