Subnetting & Supernetting

Optimizing the assignment of IP addresses

Subnetting

In supernetting, each organization is assigned a single CIDR network identifier that represents a single network. However, working with a single large network is not efficient due to factors such as unnecessarily high traffic on the network.

To reduce unnecessary traffic on the internal network, an organization can use routers to physically segment the network into subnets. Since each subnet requires its own network identifier, the CIDR network identifier assigned to the organization can be split into smaller network identifiers for each subnet. The process of splitting a network identifier into smaller network identifiers is known as a Subnetting.
The smaller network identifiers are also referred to as subnet identifiers.
In the example above, once the organization has been assigned a single network identifier, it can divide its network into smaller segments as needed. The organization uses a corresponding subnet mask for this purpose. After physically segmenting the network, it must be ensured that the network is logically divided into subnets and that a subnet is created for each network segment.
The organization then assigns each subnet an internal network identifier, the subnet identifier, according to the number of computers it contains.
However, because subnetting is an internal, network-specific process, routers outside the organization's network do not see the individual subnets and their subnet identifiers.
In the example, if the organization does not want to include more than 62 computers in each subnet, it could use the 255.255.255.192 subnet mask.

Supernetting

CIDR uses the concept of supernetting to avoid such unsuitable address assignments. Supernetting is a strategy that combines multiple addresses from the class-based environment into a single network identifier in the classless environment.

Using supernetting, CIDR combines multiple Class C network identifiers into a single CIDR network identifier. In CIDR notation, a network identifier is represented similar to an IP address by the number of bits in a subnet mask, such as 192.168.0.0/22.

In the example above, the organization can purchase a 22-bit network identifier (/22) that allows a maximum of 1,022 valid hosts, providing expansion capabilities for the current 800-computer network.

This solution does not waste a large number of IP addresses or add multiple entries to the Internet routing tables.

Calculation table for Sunetting/Supernetting

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  Available host identifiers
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  Convert to binary format
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  Determining local hosts and remote hosts
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  Organize Networks
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  Subnet Masks
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  Subnets
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  Subnetting & Supernetting
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  Subnetzmaskenbits