Newbie here just getting my head around subnetting and have a question.
When using the subnet mask to identify the network portion and the host portion of the subnet mask and then working out how many subnets and useable host addresses that would give us, we use the 2 to the power x -2 (where x is the number of bits used for the host or network portion).
I fully understand the 2n-2 for the host addresses as the -2 represents the network address and the broadcast address, however I don't understand why we need to do -2 for the amount of subnets available.
An example question I've found on sample CCNA test papers and CBT courses is when a class C address is given with a 28 bit mask and you are asked to work out how many subnets and how many usable host addresses you would get. You are given multiple choice answers - one of the answers is usually 16 subnets with 14 usable host addresses and one of the answers is 14 subnets with 14 usable host addresses (plus 2 other irrelevant answers)
I'm happy with the 14 usable host addresses using the 2n-2 formula, but the correct answer according to the papers/course is 14 subnets - again this makes sense using the 2n-2 but I am just not sure why we should be using the -2 bit of the formula when calculating subnets? Why isn't it 16 subnets with 14 usable host addresses?
Will probably be very obvious and I've missed the point completely.