Why do ISPs change your IP address?

Why does IP change? If you rely on any sort of service that requires you to know the IP address of your home internet connection, there’s a good chance you’ve noticed that the number (however frequently or infrequently) changes. Why is that?

Know Why...!!!

Infact, ISP's don't change your IP address, they just forget your last assigned address after a period of non-use. 

1.The reason that the ISP releases your address to the pool is because there are more potential devices than the pool of addresses could handle. Most large ISP's have a Class-A IP range which means they can subassign 16,777,214 unique IP addresses. AT&T, Verizon and other ISP's certainly have more than 16,777,214 customers. Smaller ISP's, usually regional cable companies get by with a Class-B ISP range which can contain 65,534 unique IP addresses. Still not enough if a cable company serves a half-dozen towns. The IPV6 protocol would provide enough unique IP addresses to give every person on earth billions of unique addresses, with 4.7994692e+29 addresses per person. We may never run out of IPV6 addresses even when every person, appliance, vehicle and light bulb gets one. The problem is that much of what is on the internet cannot yet handle IPV6. Windows 7 and 8 can handle V6 addresses as well as most ISP's, but there are still many consumer routers and upstream DNS servers that aren't ready for V6.

2.There is also a security concern. If everyone had Public IPs, then hacking your neighbor or a specific person would be much easier. Since most people don't keep track of this, having the outside IP address rotate occasionally means people just can't guess your IP. Unless there is a local app that calls home and reports your new IP to a hacker, rebooting your modem and retrieving a new IP will stop any outside traffic from gaining access to your PC. This also prevents home grown servers, as previously said.

3. There is also less hassle with dynamic. Internet Routers grab whatever IP is available out of a pool. It allows companies from having to keep a list of what they can or can't reassign.

4.  By providing two types of Ip, i.e. dynamic and static, ISPs can easily distinguish between “consumer” and “professional” services–by reserving static IPs for customers who pay more, it gives customers who need that feature an incentive to upgrade their service level.

So, there are a lot more advantages of dynamic IP than we know.. Thanks for reading :)