Hello, and this is sunny welcome back today. My topic is how to calculate the total number of usable host IDs on a network. If a subnet mask is giving, for example, what's, the total number of usable, host IDs.

You can have on a slash 24 network forests. Last 24 is the subnet mask II shorthand in binary. / 24 means the subnet mask has 24 ones, followed by eight zeros altogether. It is 32 bit long. These 8 bits of zeros are reserved for host IDs. A host ID can be signed to a host or computer or any networking. Device on a certain network to get the total number of an usable host IDs.

We use a simple formula. H equals two to the X, minus 2 where H stands for the total number of usable, host IDs, X stands for the number of zeros of a giving subnet mask in. This example, X is 8 because there are eight zeros. So we change X to eight.

We do the calculation 2 to the eighth power. We get 256. They - - we get 254. Therefore, the total number of a useful host. Ids are 254.

You might ask why - 2 let me explain - to the eighth. Power 256 is the total number our IDs on a / 24 networks. However, the first ID is a reserved for the network ID and unique identifier for a certain network. Any network has networked ID is just like every city has a zip code. And the last ID is reserved for the network broadcast ID is used by any host on a certain network to broadcast that's.

Why we must subtract two from 256, any ID between network ID and a broadcast ID can be signed to a host on a network. And we will use this knowledge. For subletting and subletting, a subnet in next two videos.

So please stay tuned. Thank you very much and see you next time.