How IP Subnets Work

When dealing with colocation hosting, the provider will usually assign the client several IP subnets to use. This can cause a great deal of confusion. An IP subnet (sub network) is a group of adjoining IP addresses that have been broken up from a group or larger IP’s. This allows the subnets to be treated individually from those preceding and following them.

Subnets can be viewed as sequential chunk of addresses, varying in range, assigned solely to the client. The size of a subnet can vary from a single address to thousands or even millions. Generally, subnets are issued in 8, 16 or 32 IP addresses depending on client request. While this has historically been a difficult concept to grasp, network and telecommunications engineers must know this topic in depth.

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Usability of IP’s

Once issued a subnet, not all IP’s within the range have the ability to be used as hosts. Several of the IP’s are not utilized for internal networking tasks which will be separated as the network address indicating the first address in the range. The middle address in the range is known as the gateway address. The last address is the broadcast address. Consequently if 16 IP addresses are issued, only 13 will be available for use.

The Size of the Subnets

The number of IP’s that are issued is established through the use of a network mask. This is the numbering string notation commonly used by IP addresses. The longer the network mask, the smaller the subnet and thus fewer usable IP’s. A long mask black’s out more of a range while a smaller mask black’s out less of a range allowing for more IP’s.

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Subnet Example

Subnets conform to the following example:

This is a similar notation to an IP address with the addition of the ‘/’ then a number. The last number is indicative of the length of the subnet mask.

IP Classes

There are three classes of IP subnets; class A, B, C, D and E. Class A is used in fifty percent of the internet. Class B is used in twenty-five percent of the internet. Class C is used in a twelve percent of the internet. Class D is used in a six percent of the internet and class E is used in three percent of the internet.

While this is a basic understanding of subnets, the origins and calculations of actually calculating a subnet can be quite difficult. While many individuals have a difficult time with this concept, subnet’s are vital every network from the smallest local network to the largest global network. By understanding the inner-workings of this difficult topic, both the customer and the website will benefit in the long run.

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