Microsoft Certified Systems Engineer (MCSE) Question:

Subnet mask is use to isolate the network ID and Host ID. e.g. - if an IP is 192.168.0.1 then the default subnet is 255.255.255.0 because it is a C Class Address C Class Add. Have three network octate and one host octate i.e.

Network ID: 192.168.0.0

Host ID : 0.0.0.1