IP Math’s

Now create a new row after this for the Subnet address, again we are only interested in the last octet which is ‘240’. For this tough you will need to place a ‘1’ in the column for the 240 and all the fields to the left of this, this will then look like the following table.

Now you need to draw a line under this and using binary maths, which is very simple, we need to work out the ‘Network Address’, this address is not useable by users on the network, but lets us know what the address range is. For example a standard Class C address of 192.168.0.0 / 24 (IP address 192.168.0.0, Subnet Mask 255.255.255.0) would be explained as:

So now for the math’s bit. all that you need to remember is the following table.

So taking this into account you should now have a table that looks like this.

This tells us that the first network address is 64, or to be precise 142.168.45.64

Now we need to make the final calculation, this will give us the ‘Broadcast Address’, for this we will need to first add a new row under our last and call this ‘The Broadcast Address.

Now, we know that the IP address used is also on the subnet range of 255.55.255.240, and we know that we are only really interested in the last set of numbers, i.e. .240, and because of this we need to enter a ‘1’ in all of the boxes to the right of the 240 (The Subnet row), this should look like the following table.

Now to finish this, using the same math’s that we did earlier, look at the remaining four empty boxes at there respective columns, work this out, and this should look like the following table.

Finally we need to take these last two rows and convert them back to numerics thus.

So, after all this, what do we know?

We now the following: