Subnet Masks Reference Table

Subnetting is the process of dividing one network into smaller networks. Collectively, the smaller networks are referred to as subnetworks (or subnets), and the singular subdivision is a subnetwork (more commonly referred to as a subnet). Every single computer that is connected to a subnet shares an identical portion of the IP address. This shared information is known as a routing prefix, and in IPV4 (Internet Protocol Version 4), the routing prefix is called a subnet mask. The subnet mask is a "quad-dotted decimal representation".

This IPv4 Subnet Chart can assist you in looking up how a network is broken up into subnets.

Class address ranges:

• Class A = 1.0.0.0 to 126.0.0.0
• Class B = 128.0.0.0 to 191.255.0.0
• Class C = 192.0.1.0 to 223.255.255.0

Reserved address ranges for private (non-routed) use:

• 10.0.0.0 -> 10.255.255.255
• 172.16.0.0 -> 172.31.255.255
• 192.168.0.0 -> 192.168.255.255

Other reserved addresses:

• 127.0.0.0 is reserved for loopback and IPC on the local host
• 224.0.0.0 -> 239.255.255.255 is reserved for multicast addresses

Chart notes:

• Number of Subnets - "( )" Refers to the number of effective subnets, since the use of subnet numbers of all 0s or all 1s is highly frowned upon and RFC non-compliant.
• Number of Hosts - Refers to the number of effective hosts, excluding the network and broadcast address.

Class A

Class B

Class C

Class D