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Now we will put our host bits to work! Remember we had 5 bits to use for host addresses. Now we put them to work. Host bits will signify a broadcast, which is all 1s, and all 0s is an illegal address. So let us give our first 3 networks addresses! Network Address First host address we ad a 1 at the end of the last octet. Now to find our last address in the network we add all ones except for the last bit in the host section. Now to find the broadcast address, we must add all 1s in the host address section (last 5 bits in this case). Now you can see that the 30 host addresses are noted from 33 to 63. 63 is your broadcast address which when this address is used, packets are sent to every address on that network, in this case everyone on the 192.168.46.32 network. Now given the example, you should be able to find the first, last, and broadcast addresses for the 64 and 96 networks. Network address First host Last host Broadcast Address Network address First host Last host Broadcast Address You can check these by entering the binary equivalent into your calculator; it is a good way to double check it that way. Having each of the networks, and address space set out we then can put them to work within the network. When using the 32 network, 192.168.46.33 – 192.168.46.62 are used for nodes on the network. It goes the same for each network. You can only use the addresses within the first and last host address. That is why we find them, so we can designate the addresses. You can also work the other way, let's say your boss says you need to create a subnet to hold 600 nodes. You would just work backwards from you did with finding networks. Find how many octets it would take to hold that many hosts using the equation given before. You then can see how many network bits you have left, and you will know how many subnets you can have that will hold 600 hosts. After reading this I hope you got a grasp on the concept of subnet masking and assigning address spaces. I hope you have learned something, whether it was just the binary/decimal part or actual subnetting. No longer should subnet masking give you a sigh, or a gasp of WHAT DO I DO! But rather a sigh of relief that you know what you are doing. This is a big part in networking, so if you do not enjoy it, it may steer you away from the field, or draw you in with the challenge it lays out. Overall, I hope this gave you an idea about subnet masking and what it is all about. Now I will leave you with a problem for you to work out, the answers will be given but this is a challenge to you to see what you have learned. The problem is: You now work at SuperFast networks, and you were asked to create a network with the following address class B address: 10.5.0.0/16 remember the /16 is equivalent to the subnet mask of 255.255.0.0. You have to create a subnet of 1000 networks. Give me the new subnet mask, and how many hosts this will give you Answer: 10.5.00000000.00000000 This gives you 16 bits to work with. 2 10 (bits) - 2 = 1022 networks, this is plenty to give you the 1000 asked for. This makes it 10.5.11111111.11 | 000000 255.255.255.192 or /26 2 6 (bits) – 2 = 62 host addresses for each network The new subnet mask is 255.255.255.192 or /26 And there are 62 host addresses for each network  |
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