Supernetting is a way to treat a group of smaller network blocks or subnetworks as one large network, allowing for customization of network size and reducing demand on routing equipment. It replaces the previous class addressing system and has drawbacks such as higher complexity and the need for new routing protocols. CIDR notation is used to distinguish between network and host identifiers.
A supernet is a group of computer networks or subnetworks that are treated as a single entity. The concept was created in response to the shortcomings of the “class” addressing system in which Internet Protocol (IP) addresses are distributed in pools of predefined sizes known as blocks. Supernetting allows organizations to customize the size of their networks and reduces the demand on network routing equipment by aggregating many separate paths.
With both supernets and class addressing systems, IP addresses are split into a minimum of two parts: a network identifier that specifies a network, and a host identifier that specifies a computer or other device on that network. The overall length of an IP address is limited, so the size of one identifier limits the size of the other. Before the supernet concept, IP addresses were distributed in blocks, according to a “class” that determined how much of each address was dedicated to either type of identifier. In a “class A” address, the network identifier is quite short, leaving room for only 127 network blocks, while the relative length of the host identifier allows each of these 127 networks to have over 16 million hosts . The other two common classes are class B, which can support up to 65,534 hosts and 16,384 networks, and class C, which allows only 254 hosts, but just over two million networks.
The idea for a supernet was created in response to several problems with the class addressing system. Many businesses and organizations needed more than the 254 hosts available from a Class C network block, but far fewer than the 65,534 addresses provided in a Class B block. B, but they used only a fraction of the 65,534 allocated addresses, leading to an inevitable shortage of Class B addresses. Additionally, the rapid growth of new Web sites and network destinations began to take a heavy toll on routing equipment which had to store more and more information to reach the growing number of networks and hosts. In 1993, the Internet Engineering Task Force (IETF), officially approved the supernet concept to address these problems.
Supernetting, also known as classless interdomain routing (CIDR), does away with the previous notion of classes. A supernet is essentially a group of smaller network blocks or subnetworks that is treated as one large network. Network identifiers in a supernet can be of any length, allowing you to customize the size of the network to suit an organization’s needs. Two class C blocks, for example, could be supernetted for a total of just over 500 addresses. This system also allows for route aggregation, which groups routing information for a variety of hosts or networks into a single “summarized” route.
The supernet concept has some drawbacks, notably the higher complexity in CIDR than class addressing system and the need for new routing protocols that support CIDR. The ability to customize the length of a network identifier has made it more difficult for system administrators to distinguish between a network identifier and a host identifier. To address this problem, a new style of writing IP addresses has been introduced. In this style, called CIDR notation or slash notation, a slash follows an IP address, followed by the number of bits used for the network ID. In the example 192.168.25.5/24, the first 24 bits of the address are the network identifier, while the remaining eight bits are the host identifier.
Protect your devices with Threat Protection by NordVPN
