Most operating systems and networking hardware assume that subnetting is being used (because it is so awesome). The following table gives you a subnet cheat sheet that summarizes these defaults:Įven if you do not plan to go outside of the default IP classes, you may need to express you network using a subnet mask. They always start with 255, which is not a valid first octet for any class of IP address.Įach class of IP address has its own default subnet mask. You can easily spot a subnet mask when it is represented in dotted-decimal notation. It just tells the router which portion of an IP address it should use to figure out the network ID. It doesn’t uniquely identify any device or network. Keep in mind that the subnet mask is not the same thing as an IP address. The subnet mask is always a string of ones on the left followed by a string of zeroes on the right. The more host bits you have, the more devices that can connect to your subnet at the expense of the total number of sub networks you can set up, and visa-versa. A subnet mask works like a filter with the mask identifying the IP address bits that represent the network ID with a 1, and the bits that represent the host ID with a 0. This trick is accomplished using a subnet mask, another 32-bit number. Creating multiple networks partitions allows you to confine traffic and network breaches or virus outbreaks.Ī subnet mask defines which chunk of an IP address is the host ID and which portion is the subnet network ID. To make IP networks more secure and easier to manage.Running lots of network devices on the same subnet can gum up the works, especially if there’s a lot of broadcast traffic. To more efficiently allocate a limited IP addresses from a limited range.Here is a brief summary of the main benefits of subnetting: You may feel compelled to subnet for many reasons. For more information, read Supernetting explained. You can refer to this supernet using a Classless Inter-Domain Routing (CIDR) prefix. The opposite of subnetting is supernetting, where you combine two or more subnets to create a single, supernet. Subnetting allows you to have more control over the length of the network ID portion of an IP address beyond the bounds of the standard 8-, 16- or 24- bit lengths, so your network ID can have any size your heart desires and you have more say over the number of host devices per subnetwork. However, in many cases, standard sizes do not fit all. With standard IPv4 address classes, there are three network ID sizes: 8 bits for Class A (which allows for more hosts), 16 bits for Class B, and 24 bits for Class C (which allows for more sub networks). The number of bits you assign to the network ID allows for either a greater number of total subnetworks or more hosts (devices that can be part of each subnet). This is accomplished by manipulating the 32-bits available in an IPv4 address, which can be divided into two parts: a network ID and a host ID. IP subnetting is a method for dividing a single, physical network into smaller subnetworks, or subnets for short. Read on to better understand the point of the process and how it works, and click through to read more in-depth networking articles. While there are many benefits to subnetting, it can be confusing. Subnetting is a concept that helps you allocate IP addresses efficiently on a computer network.
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