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Internet addresses

Any computer connected to the network (no matter the Internet or local area network) has a unique email address, the Internet uses an IP address, it consists of 4 numbers separated by dots, for example: But in order to make it easier to remember, the addresses are written as a domain name consisting of several parts that determine the ownership of the resource. For example, at you can see that the resource is in the first-level domain. Ru , on the server

Domain level 0 ... for example, two entries: and
The final point (after com) is called the root domain, or the zero-level domain, this is a database distributed to previously known servers around the world, which contains a list of all first-level domains, such as com., Net., Ru. etc

Level 1 Domain:
These are all country codes (ru, uk, fr ..) as well as com. net. org. ...

The address recorded in numerical form can be transferred to the domain name and back using the Resolve utility, which is in the program Internet maniac

IP address

The IP address (v.4) is 4 digits, each digit can be from 0 to 255. The whole address consists of a network identifier and a host identifier. For example, 121 . 13.54.211. 121 is the network ID, and 13.54.211 - host identifier, i.e. at this address you can see that the computer is on the subnet 121 (see table 1-126 is the address of class A and read about it), and the company's own address is 13.54.211

There are 5 classes of IP addresses, differing in the number of bits in the network number and the host number. Those. depending on which digit (octet) the address begins, it will be of such class. The address class is determined by the value of its first octet. In addresses of different classes, network and node identifiers are defined differently, for example, in a class A address, the network identifier is the first octet, and the rest denote nodes (individual computers), that is, it turns out that there are few networks, but they are large; the network identifier already includes two octets, i.e. there are more networks in this address space than in A, but networks are smaller in size because the node identifier consists of two octets, etc.

Class IP address Network id Node ID
A abcd a bcd
B abcd ab cd
C abcd abc d

Class A addresses are intended for use on large public networks. They allow a large number of node numbers.
Class B addresses are used in medium-sized networks, such as universities and large companies.
Class C addresses are used on networks with a small number of computers.
Class D addresses are used when referring to groups of machines, and Class E addresses are reserved for the future.


The range of values ​​of the first octet (in the text highlighted in yellow)

Possible number of networks

Possible number of nodes





















In a local network, all computers work through a proxy server (the computer through which all the others are connected), therefore for the "external Internet" all computers have the same IP address, but in fact this is not the case.