Network (and also the address of subnet 0, 192.168.12.0) Now we start calculating subnets Subnet Mask (255.255.255.240) Now we calculate the resulting subnet mask: Since the main network address is already selected by the main office, we will directly start calculating the block sizeīlockSize= 12+2 rounded-up to the nearest power of 2. The number of hosts is shown in the diagram below. The headquarter’s IT manager said that you need to use the network address 192.168.12.0 with the default subnet mask (255.255.255.0). You have been assigned the duty of subnetting a network for an organization’s branch office. Again following-up on the previous example in 1, and 2, for subnet 0 the subnet address is 192.168.0.0 and broadcast address 192.168.0.15, then the usable host range is 192.168.0.1-192.168.0.14 Usable host range is simply all addresses between the subnet address and the broadcast address.In follow-up of the previous example in 1, if subnet 0 address is 192.168.0.0 and subnet 1 is 192.168.0.16, then the broadcast address of subnet 0 is 192.168.0.15. Broadcast address of each subnet is the last address before the next subnet.Subnet mask for each subnet was earlier calculated in Step 2.You can see in the table that the subnet addresses are calculated by adding 1 to the network-part of the previous subnet address. Network (and also the address of Subnet 0, 192.168.0.0) Remember to do the addition in binary, so that carry bits can be pushed to the next octet (8-bits) on the left. Next subnet address can be easily calculated by adding 1 to the network part of the previous subnet address. The first subnet address is usually the main network address. The first thing to do is to re-order subnets in according to their BlockSize in descending order. Now that we know the subnet mask, we will need to find the rest of the parameters (subnet address, broadcast address,…etc) S/N No Now you can produce the subnet mask by starting (from the left) with NBits ones and HBits zeros afterwards. This means that only HBits number of bits will be used for host addresses and the rest of the bits will be used for subnet addresses.įrom that, you can easily calculate the number of bits used for subnet address (lets call it NBits) by: Using the BlockSize that you have calculated in Step 1, you can find the number of bits required for host address after subnetting (Lets call it HBits) by the following calculation: Step 2: Choosing the Subnet Mask for Each Subnet Since subnetting mostly happens for LANs, the addresses that we will use are in the Private ranges of each class as shown in the table:įor the sake of simplicity, we usually choose 192.168.0.0 for Class C, and 172.16.0.0 for Class B.If the result is more than 2 16, go for Class A. If the result is higher than 2 8(which equals 256) but less than 2 16 (which equals 65,536), go for Class B. If the sum is 256 or less, you can go for Class C address. Note: We put +2 because the subnet address and the broadcast address cannot be used by hosts. Now we have the BlockSize for each subnet. When we say “round to the next”, it means that 17 is rounded to 32 and 5 is rounded to 8. of Hosts +2 and rounding it to the next power of 2 (ex: 2, 4, 8, 16, 32, 64.etc which is actually 2 1, 2 2, 2 3, 2 4, 2 5.etc). The BlockSize is calculated by taking the No.If it is up to you to choose the network address and IP address class, you may select it based on the following steps: If you were given a specific network address to use in subnetting, jump to step 2. Subnetting generally means using some bits of the host address to generate subnet address. What we will do in the process of subnetting is identifying the subnet address, subnet mask, subnet broadcast address, range of available host addresses for each subnet. To start with, we will assume that you have a specific number of subnets with a specific number of hosts in each subnet. Grab a pencil and a piece of paper and let’s go. After the detailed steps, we will go through two completely solved example and three more unsolved examples for you to solve. If you’re looking for classful subnetting, you checkout my other tutorial here. In this tutorial, we will go through steps of subnetting a network address using multiple subnet masks.
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