Modern Internet networks are usually based on 32-bit IP addresses, which consists of two parts - the network identifier and the host. Two methods have been developed to determine which part of the address is the host and which represents the network. Internet service providers are now using classless addressing based on subnet masks. Network classes are the first, outdated method that was based on ranges.
The IP address of any object, whether it is a server or an ordinary computer, is closely related to the network name. A special DNS service that manages domain names translates this name into a network address. Only the server registered in this service will “respond” to the network name. The resources of such servers automatically become public, and you can use them via the Internet.
Having dealt with IP-addresses, we pay attention to the classes of networks. There are five in total, and each has its own characteristics. Class A is used for huge global networks. Included in it is the Internet. The range of this class extends from zero to 127 and consists of 126 networks. One A-network accommodates over sixteen million nodes. Actually, the network identifier takes only the first eight bits, the remaining 24 bits are for the host address.
The class of networks B consists of medium-sized grids that occupy the address range up to the value 191. Here the IP address is divided into identical 16-bit parts.
One part is occupied by the network identification number , and the other is allocated to the host. The B-network integrates 65534 nodes. As a rule, it is used in universities or in large enterprises.C . 223. 24 , 8- . - 256 , IP-. , . «», «».
. D- 239. , IP-. . 255, .
All of these classes have address blocks reserved for private use. They are used exclusively in private local networks, so these addresses are not routed on the Internet and are called "gray", or "private". A NAT router is used to join private LANs and access the World Wide Web through them.
Since the above network classes have a limited number of IP addresses, it is inconvenient to use them. An alternative was a method in which the number of bytes is not limited and a subnet mask is used. However, the old system was not forgotten at all. It is described in many textbooks, and class D and E addresses are still used privately.