What is a subnet mask ?

Question

what is a subnet mask? what does it do ?

Answer 1

divides an ip address into a network part and a host part. tells routers and switches where to direct network traffic.

Answer 2

A sub net mask allows you to identify which part of an IP address is reserved for the network, and which part is available for host use. If you look at the IP address alone, especially now with classless inter-domain routing, you can't tell which part of the address is which. Adding the sub net mask, or net mask, gives you all the information you need to calculate network and host portions of the address with ease. In summary, knowing the sub net mask can allow you to easily calculate whether IP addresses are on the same sub net, or not.

Answer 3

Subnet mask divides an IP address in two parts: network mask and an address of a host in the network. ...

A mask that is used in the IP protocol to separate the subnet address from the local IP address. The IP protocol performs a bit-wise AND on the IP address and the subnet mask. Each address segment represents one byte, where 255 converts to FF hex. For example, if the IP address is 192.009. ...

The subnet mask is used to determine where the network number in an IP address ends and the node number in an IP address begins. A node is anything on a network that needs an IP address to communicate (a PC, server, router, etc).