Subnet Class

How To Use Subnet Class Tool

  • Input valid IP address in dotted-decimal format. Invalid input will show no results.
  • The class of the subnet will determined automatically.
  • Subnet class tool will not only show subnet classes ranging from A-E, but also special cases - "This" host, "This" network, loopback and broadcast.
  • This tool will show address range for each class.
  • Bit-wise representation of the IP address and class combination will also be shown. You can easily check bit usage for each class. Letter "n" stands for network bits, "h" for host bits and "x" is open type bit.

Classful network description

Classful network is a network addressing method replaced by CIDR addressing in 1993. Classful addressing was introduced in 1981 and is described in RFC 791. Network prefix is determined from IP address and its class. Obsolete IP version used 5 network classes:

Class First bits Class address range Subnet mask Routing prefix Use
Class A 0 0 - /8 General
Class B 10 128 - /16 General
Class C 110 192 - /24 General
Class D 1110 224 - Multicast
Class E 1111 240 - Reserved/Experimental

Private network

Nowadays classful network concepts can be used in private networks. With help of network address translator (NAT), private IP addresses can be translated to public addresses and vise versa. Table of private IP address ranges:

Block Range Host ID size Number of Hosts
24-bit - 24 16,777,216
20-bit - 20 1,048,576
16-bit - 16 65,536
More information can be found in RFC 1918.

To do classful subnet calculations use Subnet calculator. To do classless calculations use CIDR calculator. To calculate supernets use Supernet calculator.