6.4. IP Subnetting

Assume that an organization has three networks in three unique structures, all associated by a 64 Kbps ISDN join. Every network has around 25 nodes. Every building has its own particular arrangement of servers and printers for the employees in that building. The ISDN join between the networks is for the incidental need to transmit data between structures, for example, email messages or bookkeeping dealings. By what means ought to the organization allocate IP addresses in this circumstance?

The organization could ask for a solitary Class C set of locations, and afterward dole out those locations over the three networks in some design. This appears like a basic arrangement, however it's really a poor thought for a few reasons. Ordinarily, a considerable measure of network movement is sent to every host-ID inside a solitary net-ID. The moderate ISDN join between the structures would turn into an enormous bottleneck in this circumstance, and the entire network will not work effectively.

A further thought is to utilize separate Class C addresses (net-IDs) for every building. This is a moderately basic arrangement, and it would work fine, aside from that the ISP won't not have the capacity to relegate three separate Class C addresses. Likewise, it would be appallingly inefficient of the accessible pool of IP locations. In this circumstance, every building would squander more than 200 locations for reasons worthless.

Imagine a scenario in which there was an approach to separate a Class C address so that every building could have its own particular virtual net-ID. Such an answer is the thing that subnetting is about. Subnetting permits you to subdivide a host-ID range (normally that of a Class C address, yet such subnetting should likewise be possible with Class A or B addresses) crosswise over two or more networks. Subnetting is made using subnet masks, which are examined in the following segment.