Subnet Mask

In computer networks that use the Internet Protocol, a subnetwork or subnet is a range of logical addresses within the address space that is assigned to an organization.

For example, suppose a lighting network consists of gateways named Arthur and Trillian, connected to a switch, and then a computer. The lighting network is configured as a subnet.

Address 10.101.50.101 is assigned to Arthur, and 10.101.60.102 to Trillian. The subnet has been configured so that the first two octets of its members' addresses are all the same subnet id, 10.101, and this fact is expressed by the subnet mask 255.255.0.0

A subnet mask of 255.255.0.0 is standard/default for ETC lighting networks, however, yours may vary.