IP address - (Internet Protocol )is an very important part in the networking communication between the pears in the computer network. For a large network IP address in assigned by the Network Administrator who has the responsible for the entire network. Even though it is assigned by network administrator it could be a local network that have some user level privilege to change there IP address from a IP pool in there own machine which is inside a local network. Even if you're part of a small network routed through a single IP address, the people outside your network can see only the IP address of the gateway you're using. If you're connected directly to the Internet cloud, it's basically the same thing. You're reaching out to a certain service through a certain IP address. Why we need to change the Local IP address in the user machines? If someone would want to deny your access to certain services (an IRC channel, a certain forum, some restricted websites, game servers and so on), they'd have to ban your IP address through the proxy. The first thing that comes in mind is to change your IP address so you can evade the ban. You can wish to change your IP address due constant flooding or spam you're being the victim of.