Private IPv4 addresses
The Internet Engineering
Task Force (IETF) has directed the Internet Assigned
Numbers Authority (IANA) to reserve the following IPv4 address ranges for
private networks:
|
RFC1918 name
|
IP address range
|
number of addresses
|
host id size
|
mask bits
|
classfuldescription
|
|
|
24-bit block
|
10.0.0.0 – 10.255.255.255
|
16777216
|
10.0.0.0/8 (255.0.0.0)
|
24 bits
|
8 bits
|
single class A network
|
|
20-bit block
|
172.16.0.0 – 172.31.255.255
|
1048576
|
172.16.0.0/12 (255.240.0.0)
|
20 bits
|
12 bits
|
16 contiguous class B networks
|
|
16-bit block
|
192.168.0.0 – 192.168.255.255
|
65536
|
192.168.0.0/16 (255.255.0.0)
|
16 bits
|
16 bits
|
256 contiguous class C networks
|
Although the standard for class A and class B
networks specify 8- and 12-bit masks respectively, it is common to subdivide
these and assign other masks internally, resulting in a number of smaller
subnets (e.g. 10.0.0.0/24, with room for thousands of 254-host subnets).