What is a subnet mask, and how is it used?
If you read through the many definitions of subnet that http://www.google.com/search?hl=en […] 034;Google comes up with, you should get the gist that a subnet is a mechanism that allows network administrators to group devices on a network in order to localize data traffic for both privacy and network traffic control purposes. A subnet mask is a number in “dotted quad” format (four groups of three decimal digits) that tells network routers which bits of an IP address to look at when deciding where to route a packet of data. The 255.255.255.0 subnet mask that most of us are familiar with allows for a grouping of 253 devices (addresses with all 1’s or all 0’s are not useable device addresses). The subnet mask you use is generally determined by how the routing is set up at the level above your LAN, i.e. your ISP. Most small networkers don’t have to deal with the calculation of subnet masks unless they want to set up a network with multiple routers and subnets. More info in this http://se
