Difference between subnet and supernetting

Subnet vs Supernetting

The subnet is the process of dividing an IP network into sub-divisions called subnets. Computers belonging to a subnet have a common group of the most significant bits in their IP addresses. Thus, the IP address would be divided into two parts (logically), as the network prefix and the idle field. Supernetting is the process of combining multiple subnets, which have a common Classless Inter-Domain Routing (CIDR) routing prefix. Supernetting is also called route aggregation or route synthesis.

What is the subnet?

The process of dividing an IP network into subdivisions is called a subnet. The subnet divides an IP address into two parts as a network (or routing prefix) and in the idle field (used to identify a specific host). The CIDR notation is used to write a routing prefix. This notation uses a forward slash (/) to separate the starting address of the network and the length of the network prefix (in bits). For example, in IPv4, 192.60.128.0/22 ​​indicates that 22 bits are allocated for the network prefix and that the remaining 10 bits are reserved for the address of the host. In addition, the routing prefix can also be represented using the subnet mask. 255.255.252.0 (11111111.11111111.11111100.00000000) is the subnet mask for 192.60.128.0/22. The separation of the network portion and the subnet portion of an IP address is accomplished by performing a bitwise AND operation between the IP address and the subnet mask. This would result in the identification of the network prefix and the host identifier.

What is supernetting ??

Supernetting is the process of combining multiple IP networks with a common network prefix. Supernetting has been introduced as a solution to the problem of increasing the size of routing tables. Supernetting also simplifies the routing process. For example, the subnets 192.60.2.0/24 and 192.60.3.0/24 can be combined in the subnetwork designated by 192.60.2.0/23. In the over-network, the first 23 bits constitute the network part of the address and the other 9 bits serve as the host identifier. Thus, an address will represent several small networks, which would reduce the number of entries to include in the routing table. Generally, supernetting is used for class C IP addresses (addresses starting from 192 to 223 in decimal) and most routing protocols support supernetting. BGP (Border Gateway Protocol) and OSPF (Open Shortest Path First) protocols are examples of such protocols. But protocols such as EGP (Exterior Gateway Protocol) and RIP (Routing Information Protocol) do not support supernetting.

What is the difference between subnet and supernetting?

The subnet is the process of dividing an IP network into sub-divisions called subnets, while Supernetting is the process of combining multiple IP networks with a common network prefix. Supernetting will reduce the number of entries in a routing table and also simplify the routing process. In the subnet, the host ID bits (for IP addresses of a single network ID) are borrowed for use as the subnet ID, while in supernetting, the bits Network IDs are borrowed for use as the host ID.

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