It similar to a postal code that used by a post office to route letters to a general area. It only used by the local post office to deliver the letter to its final destination. The host part of the IP address performs this same function. Hosts use the address 0.0.0.0 when they are being booted, this address is not used afterwards. Also the addresses with all zeros or all ones in the host part are reserved for special purposes.
Corporate networks tend to consist of two to three hundred computers per site.
This rigid assignment scheme has resulted in large quantities of unused but still unavailable addresses. This waste is a cause of increasing alarm in the Internet Engineering Task Force . I will return to this concern in my next article. The host part of an IP address can further be split into a sub-network address and a host address. Subnetworks permit organizations to manage groups of addresses more effectively.