Describe what a subnet mask is, and explain why it is used. Then, detail how it is used to determine the network ID of an IP address.

What will be an ideal response?

Each computer with an IPv4 address must also be configured with a subnet mask to define which part of its IP address is the network ID and which part is the host ID. Subnet masks are composed of four octets, just like an IP address. The simplest subnet masks use only the values 0 and 255. An octet in a subnet mask containing 255 is part of the network ID. An octet in a subnet mask containing 0 is part of the host ID. Your computer uses the binary process called ANDing to find the network ID. ANDing is a mathematical operation that compares two binary digits and gives a result of 1 or 0. If both binary digits being compared have a value of 1, the result is 1. If one digit is 0 and the other is 1, or if both digits are 0, the result is 0. When an IP address is ANDed with a subnet mask, the result is the network ID.