Network what is a subnet

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Most Popular. For example, The network subnetting scheme in this section allows for eight subnets, and the network might appear as:. Notice that each of the routers in Figure 2 is attached to four subnetworks, one subnetwork is common to both routers.

Also, each router has an IP address for each subnetwork to which it is attached. Each subnetwork could potentially support up to 30 host addresses. This brings up an interesting point. The more host bits you use for a subnet mask, the more subnets you have available. However, the more subnets available, the less host addresses available per subnet. For example, a Class C network of If you use a mask of Since you now have four bits to make subnets with, you only have four bits left for host addresses.

So in this case you can have up to 16 subnets, each of which can have up to 16 host addresses 14 of which can be assigned to devices. Take a look at how a Class B network might be subnetted.

If you have network Extending the mask to anything beyond You can quickly see that you have the ability to create a lot more subnets than with the Class C network. You use five bits from the original host bits for subnets. This allows you to have 32 subnets 2 5. After using the five bits for subnetting, you are left with 11 bits for host addresses. This allows each subnet so have host addresses 2 11 , of which could be assigned to devices.

Note : In the past, there were limitations to the use of a subnet 0 all subnet bits are set to zero and all ones subnet all subnet bits set to one. Some devices would not allow the use of these subnets. Cisco Systems devices allow the use of these subnets when the ip subnet zero command is configured.

Now that you have an understanding of subnetting, put this knowledge to use. Your task is to determine if these devices are on the same subnet or different subnets. You can use the address and mask of each device in order to determine to which subnet each address belongs. Looking at the address bits that have a corresponding mask bit set to one, and setting all the other address bits to zero this is equivalent to performing a logical "AND" between the mask and address , shows you to which subnet this address belongs.

In this case, DeviceA belongs to subnet Given the Class C network of Looking at the network shown in Figure 3 , you can see that you are required to create five subnets. The largest subnet must support 28 host addresses. Is this possible with a Class C network? And if so, then how? You can start by looking at the subnet requirement.

In order to create the five needed subnets you would need to use three bits from the Class C host bits. Two bits would only allow you four subnets 2 2.

Since you need three subnet bits, that leaves you with five bits for the host portion of the address. How many hosts does this support? This meets the requirement. Above example shows how IP addresses should be deconstructed, which makes it simple for Internet routers to find the right Network to route data into. However, in a Class A network there could be millions of connected devices, and it could take some time for the router to find the right device.

You should use the binary notation method for both the address and the mask and then apply the AND operation to get the block address. Skip to content. What is Subnetting? Report a Bug. Previous Prev. This results in the characteristic dotted decimal format for IP addresses—for example, The range of values in decimal is 0 to because that represents to in binary. Since the internet must accommodate networks of all sizes, an addressing scheme for a range of networks exists based on how the octets in an IP address are broken down.

You can determine based on the three high-order or left-most bits in any given IP address which of the five different classes of networks, A to E, the address falls within. A Class A subnet mask reflects the network portion in the first octet and leaves octets 2, 3, and 4 for the network manager to divide into hosts and subnets as needed.

Class A is for networks with more than 65, hosts. A Class B subnet mask claims the first two octets for the network, leaving the remaining part of the address, the 16 bits of octets 3 and 4, for the subnet and host part. Class B is for networks with to 65, hosts. In a Class C subnet mask, the network portion is the first three octets with the hosts and subnets in just the remaining 8 bits of octet 4. Class C is for smaller networks with fewer than hosts.

You can determine the number and type of IP addresses any given local network requires based on its default subnet mask. Subnetting is the technique for logically partitioning a single physical network into multiple smaller sub-networks or subnets.