The IP address is a unique address of the computer in IP network which is used for movement of data between nodes. At the same time delivery to the addressee is not guaranteed. In fact, the IP address in something is similar to your home postal address.
As is well-known. The IP address of the fourth version which is now used consists of 4 groups of the decimal numbers containing 3 digital characters value from 0 to 255. Groups are separated by points.
The agreement on use of the IP addresses contains data on their division on dynamic and static. The difference is in whether the constant address at the computer or changes at each connection.
The answer to a question of the reasons of change of the IP address is simple. To each provider a certain address range is selected. At access to the network, your computer receives the address. The number of the electronic computers connected to the Internet grows every year. It is natural that to assign the separate IP address to the separate machine it is simply unreal. The existing quantity of the addresses just will not be enough for all.
For this reason the decision which suited many was made. The IP address began to be given to the computer only at the time of connection to network. That is, when the computer or the modem sends request for access to the network. All IP addresses which are not used, are in a reserve at present. reset of the modem, break of communication or restart of the computer to you the new IP address will be assigned. At the same time, information to whom, when and what IP address was given surely is saved at provider in case of request from law enforcement agencies. Selection of the address happens "blindly", to guess what to you will drop out next time, it is impossible. At
Thus, the explanation can be only one: you have a dynamic IP address.
You remember: usually for the mezzanine board it is possible at provider it is possible to connect service according to which your IP address will become static, i.e. will not change.
Both systems have the pluses and minuses. At dynamic you can bypass the ban and also download the bigger number of files from free file hosting services. At static you will be able to work in programs which need a rigid binding to the address and also to continue downloading at break of communication on some services.