As is well known. IP address of the fourth version, which is now used consists of 4 groups of decimal numbers each containing 3 numeric characters from 0 to 255. Groups separated by dots.

The agreement on the use of IP addresses provides information about the division into dynamic and static. The difference lies in the fact that the permanent address for the computer or is changing each time you connect.

The answer to the question on the reasons for changing IP addresses is simple. Each provider is allocated a specific range of addresses. When access to the network, your computer gets the address. The number of computers connected to the Internet, grows every year. Naturally, to secure a separate IP address for separate machine is simply unrealistic. The existing number of addresses is simply not enough at all.

For this reason, it was decided that many arranged. IP address was issued to the computer only when I connect to the network. That is, when the computer or the modem sends a request for access to the network. All IP addresses that are not currently used, are in reserve. restart the modem, connection is broken or the computer is restarted you will be assigned a new IP address. At the same time, the information of who, when and what IP address has been necessarily preserved from the provider in case of request from law enforcement agencies. The allocation of the addresses takes place "blind", guess what you get next time, impossible. When

Thus, the explanation can be only one: you have a dynamic IP address.
Remember: usually a surcharge from the provider to activate the service, in accordance with which your IP address will be static, i.e. will not change.

Both systems have their pros and cons. With dynamic you can get around the ban, and also download more files from free file sharing. If static you will be able to work in programs that need a hard peg to the address, and to continue downloading when connection is broken on some services.