SUBNETTING

TCP/IP - Subnetting

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I can recalled during my reprofiling days, we do came across subnetting. Back to current, in day 1, AM session, Mr Foo touch on the subnetting, I really can't catch how he derive the number of subnetting give the number of subnetting that are needed for a network.At home, I spent one hour of self study on the note given, and I managed to grasp a little. Not till the next morning (Day 2) before going to class, I managed to fully understand how to derive subnetting. What Is Subnetting Subnetting is the process of allocating bits from the host portion as a network portion. For example, giving the class A network 10.0.0.0 a subnet mask of 255.255.0.0 would break it down into 256 sub-networks (10.0.0.0 to 10.0.255.0), and indicates that the first octet of the IP address shows the network address, the second one shows the subnet number and the last two show the host part. A bitwise AND operation of the host address with the subnet mask extracts the complete subnetwork address (see example below). Subnet masks are not limited to whole octets, either. For example 255.254.0.0 (or /15) is also a valid mask. Applied to a class A address this would create 128 subnetworks in intervals of two (1.2.0.1 - 1.3.255.254, 1.4.0.1 - 1.5.255.254, etc).