Shulou(Shulou.com)06/02 Report--

When you want to choose an available subnet mask for the network, and you need to infer the number of subnets, legitimate host numbers, and broadcast addresses determined by this mask, all you need to do is answer the following five simple questions:

How many subnets will be generated by this selected subnet mask?

How many subnets? 2x = number of subnets. X is the number of digits of the mask, or the number of 1s in the mask. For example, at 11000000 clock, what we get is 22 subnets. In this example, there are four subnets.

two。 How many legitimate host numbers will be available in each subnet?

2yMel 2 = the number of hosts per subnet clock. Y is the number of bits that are not masked, that is, the number of zeros in the subnet verification code.

3. What are these legal subnet numbers?

256-Subnet mask = block size, which is the increment value. For example, 256-192-64. The block size of 192 mask is always 64. Starting from 0, 64 is used as the block to count the subnet mask values, so the resulting subnets are 0, 64, 128, 192.

4. What is the broadcast address for each subnet?

We have calculated that our subnets should be 0, 64, 128 and 192, so this broadcast address will always be next to the address of the next subnet. For example, the broadcast address of the 0 subnet is 64. The broadcast address of the 64 subnet is 127. Because its next subnet is 128, and so on. Colleagues should also remember that the broadcast address of the last subnet will always be 255.

5. What are the legitimate host numbers in each subnet?

The legal host number is the value between the various subnets and subtracts from the host number of all zero and all one. For example, if 64 is the subnet number and 127 is the broadcast address, then 65 '126 is a valid host range, that is, it is always the address between the subnet address and the broadcast address.

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