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Private IP Address Ranges

The Internet Engineering Task Force (IETF) has directed the Internet Assigned Numbers Authority (IANA) to reserve the following IPv4 address ranges for private networks, as published in RFC 1918

RFC1918 name

IP address range

number of addresses

classful description

largest CIDR block (subnet mask)

host id size

24-bit block –


single class A (

24 bits

20-bit block –


16 contiguous class B's (

20 bits

16-bit block –


256 contiguous class C's (

16 bits