Originally published at: http://www.howtogeek.com/163747/why-do-isps-change-your-ip-address/
Image courtesy of EasyDNS, a dynamic DNS service provider.
Also because sometimes there are more internet users than allotted ips. Mine changes everyday
And I thought 192.168 was reserved to LAN/private network..?
Mine change every 2 weeks, I will loose connection for up to 5 minutes and then the connection comes back up. My ISP can provide me with a static IP, but that is reserved for business customers. I can get one because I run computer shop out of my old garage, which thus qualifies it as a business.
ISP's don't change your IP address, they just forget your last assigned address after a period of non-use.
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. My home may be atypical, but I have more than two-dozen devices on my home network. 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.
My IP address changes every time I sign on.
my ip also changes every time i sign in or restart my modem....
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.
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.
ya , bcrail is right , its only due to security problem , if everyone gets a static ip then it will be easy to hack a neighbourhood ip.
As ISP can easily remember the ip which was last assigned, and also i dont see any other logic behind a dynamic ip.
But if you need you can always request for a stsatic IP, as your ISP can alot you a static IP by charging some extra cost
I'd like to make a few notes:
1) Yes, 192.168/16 is reserved as a private address range along with 10/8 and 172.16/12 (RFC 1918).
2) The primary reason for the address changing is not security, though it can be a side effect. For that matter, my dynamic IP has remained constant for months. As SteveMann pointed out, it's a logistics issue of more nodes than possible IPv4 addresses. IPv4 addresses are 32 bits meaning 2^32 possible unique addresses. Some of these are reserved as private or special cases/uses (RFC 5735). This still leaves a large block of addresses that can be used as public where any node in the internet can address another publicly without masking or other tricks. However, with the explosion of modern day computers we have very quickly made more devices than the amount of available public addresses. With practically everyone being on the internet and usually having more than one device (such as a laptop and a phone) it quickly became apparent we would need far more addresses, especially with the anticipated explosion of IP devices. It's expected that soon all sorts of small devices will need their own IPs such as for surveillance or even your toaster. So IPv6 came around which uses 64 bits and dramatically increases the amount of possible unique addresses. The problem now is that the internet's infrastructure needs to update to support IPv6, which unfortunately isn't happening quickly enough. Until enough of the internet can support it the standard has to remain at v4. SteveMann explains why ISPs change addresses but there's an even bigger problem; the last IPv4 blocks have been issued (ICANN assigns its lastIPv4 addresses 3). That means every possible public IP is owned by someone. The main ICANN authority has divvied up its last blocks and now the regional registries are on their last v4 addresses and will have to recycle unused ones after exhausting those. So, major detour aside, IPv4 addresses are becoming a scarce commodity and need to be allocated from a finite size pool. Sometimes you get the same address back from your ISP, sometimes someone else gets that address.