How to change (Dynamic) IP address in Windows 7 or Vista?

*"Uh, where did I repeat what you stated and tell you what you already know?"*What I meant was you clearly read what I already stated and did'nt just tell me what I already knew, like the other person who replied and did exactly that, which I was expecting to have happen and hence the reason I tried to be clear that such an answer wasn't going to solve the problem, hopefully before anyone wasted time trying to reply with an answer that was already tried. I guess I could have written that better, this...

"Thanks for taking the time to actually read what I already stated before just telling me what I already know Jim, appreciated."

Should have read more like this...

Thanks for taking the time to actually read what I already stated AND NOT just telling me what I mentioned does not work Jim, appreciated.

"You don't say what you're doing that requires cycling IP addresses, but assuming that it's guaranteed to be different from DHCP is just unsupportable.  Assuming that DHCP is offering some meaningful level of privacy and security is placing your hope in the wrong place."

Does it make a difference why I'd want to change my Dynamic IP at will? Will this in some way make the difference of someone knowing how Windows is now storing this info or not?

If it wasn't an added layer of both privacy and security then why would any given web browser made allow for deleting cookies? Does it really do any good to clear cookies to protect your privacy and browsing history from data miners if your system maintains the same exact IP address. Allowing a person to change their IP is more significant on the protection of privacy than clearing cookies.

On the matter of security it again makes a significant difference. If someone was determined to hack a persons home PC then this effort would significantly be simplified if such a person always knew what exact IP they were looking for in an effort to make repeat attempts at determining exploitable holes in the particular system. Since no one has yet to develop the holy grail of computer security we are left to still rely upon multiple layers of protection. The ability to constantly alter your systems public known IP address is just one layer of security that can be used to make such an effort more difficult. Its pretty hard to target and probe a specific computer if its known address becomes unknown.

Any how...

I think the dirty, yet to some degree scientific approach I have made certainly proves my DHCP server is a bit more than luck of the draw in assigning a different IP upon request when under other OS's I can change the IP all day long and not be assigned a repeat address, yet under Vista and Win7 the issue of reassigning the same exact IP can also be reproduced every single time. It seems clear here that the thinking behind this change was just yet another effort to dumb down networking confusion for dumb users. The problem I have with this was its now made a significant hole in both privacy and security efforts for individual users. Someone at Microsoft needs to let those of us who aren't just dumb users know how to take back our own control of our privacy and security concerns.

Uh, where did I repeat what you stated and tell you what you already know?  I did not see anything in your writing about the DHCPDISCOVER behavior and didn't myself know that it allowed a request for the old address until I looked into it further.  Maybe you had read that elsewhere, but that sure wasn't obvious in this thread.

Might I also point out that when the DHCP servers "reassign a new address" at midnight, or by request, or whenever, that "new" doesn't necessarily mean "different".  Nothing in DHCP guarantees it'll be different, and that you are seeing this on XP and Linux is just a likely thing because of your specific DHCP server, not a guaranteed thing. 

You don't say what you're doing that requires cycling IP addresses, but assuming that it's guaranteed to be different from DHCP is just unsupportable.  Assuming that DHCP is offering some meaningful level of privacy and security is placing your hope in the wrong place.

On my own (Win7) DHCP system I found my current IP address in numerous places in HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\Tcpip\Parameters, including under Interfaces that you mention, but also under DNSRegisteredAdapters (see HostAddrs, it's in there in binary form).  I've no idea which of these, if any, might be used by DHCPDISCOVER.

Jim

Thanks for taking the time to actually read what I already stated before just telling me what I already know Jim, appreciated.

My service is wireless broadband (Clear Wire), the modem does not act as a router and I'm not using any kind of router, nor does my system have any kind of local (196.xx.xx.xx) type IP.

Everything you said seems to be exactly in line with what I thought I already knew, probably the main reason this entire thing is bugging me so much. I would agree, the DHCP server, in this case my ISP service, is in control of assigning the IP address.

Just to help you out, I'm not a guru, but I have been using computers since Windows 3.11 was around, and come from the days when all network connections had to be configured manualy by the user, so I'm not coming from complete inexperience either. I've done all this a couple few times.

I've argued this point about the DHCP server assigning my IP with my ISP, I even had my complaint escalated to a higher level support. Their answer to me was their DHCP servers reassign new IP addresses every night around midnight. They also said my computer may be requesting a specific IP and if its available then it will allow this request.

This seems to be exactly what's happening. What's new to me in Vista and 7 is the computer deciding to make this request, and worse, not allowing me control over changing it. Like I said, I can plug in an XP laptop to this same modem, get a dynamic IP assigned to it, then at a prompt just run IPCONFIG /RELEASE followed by a /RENEW and instantly obtain a fresh IP. I can do that all day long with no problems, yet, as soon as I plug this once Vista (now 7) laptop in it doesn't work, even if I select to open the CMD prompt "As Administrator". It just hangs onto the same exact IP address.

Theory 2 that I also shot full of holes was maybe the DHCP server is recognizing the MAC address of my NIC card and always assigning the same IP to it. This can't be the case though, I tested this theory out and it doesn't work. Using an Ubuntu boot disk I booted the same Win7 computer into Linux, with the same exact MAC address on the NIC I am given a different IP, and can change it at will in Linux by releasing and renewing the IP assigned to me.

So, from what I do know, and have ruled out by trying, is some how, somewhere Vista and 7 seem to be storing assigned dynamic IP addresses and requesting this same IP from the DHCP server. My ISP's DHCP server must not get enough new requests to use up all its available IP's so even with the modem off for a week, when it comes back on line the same IP my computer seems to be requesting is still available and gets reassigned to me again.

If I reinstall Vista (tried this on another computer that needed a new hard drive installed), that information gets lost and a fresh IP is assigned after the Windows reinstall. Just to be certain, I even tried to force my assigned IP to be dumped and changed, couldn't be done, reinstalled Vista again just to see what would happen and it gave it a different IP.

So, what I'm trying to find out, for the sake of my own sanity, is where is Vista and 7 storing this information so I can go in and manually clear it. The registry value older versions of Windows used that I listed above is still there, yet clearing it there, or even editing a change there does not clear it, if I reboot the old IP turns right back up in there all over again.

To me, this is a significant privacy, and security concern/issue.

I have searched from one end of the web to the other looking for an answer to this, what I find are many answers telling people what I already know how to do, and what use to work perfectly under XP and prior versions of Windows. What I'm also finding are many other people now using Vista or 7 who are finding this same problem and no one seems to have an answer. With people now saying the old methods no longer work, the best answer anyone else seems to come up with is leave the modem unplugged over night, yet, this doesn't work either. I've gone even one step farther and unistalled the NIC thinking this would clear the data, yet it doesn't work either.

**Clearly Vista and 7 are storing this information, what needs to be said to answer the question is where is it being stored so possibly even an advanced user can go in and manually clear it and allow a new IP to be assigned when the DHCP server is not set up to be authorative enough to deny such a request.**I do have one solution in mind I guess I could try, but it doesn't answer the question, and I shouldn't be forced to go this route. I was thinking in theory I could plug a router into my modem and utilize a local non routable IP on the computer, allow the DHCP server to assign the WAN IP to the router, thus giving me control through my router settings in being able to force the change request and leave Windows always on just a non routable IP.

That should work, but it still doesn't answer the question I'd like to know the answer to for Vista and 7, how do you clear this data so the same IP isn't repeat requested like it seems to be wanting to do? What's even more troubling is I can't even get the answer on a Microsoft owned Windows 7 networking support forum. If Microsoft doesn't even know the answer then who does?

This has to be what's happening...

jreuter:

"Perhaps from Vista on this behavior was added to Windows, though I don't know this to be the case for certain."

The question however still remains, and is unanswered, where is Vista and 7 storing this information so it can be manually deleted to change this undesired behavior?

Tony1967, I'm very confused.  Is your dynamic network connection not working, or is it working but you are bothered by the fact that you cannot force the address to change?

If the latter, the bottom line is that your client has no control over the IP address, the DHCP server does, and there is no guarantee that you will get a different address every time you renew the DHCP lease.  That's entirely up to the DHCP server, and it can cache simple things like your MAC address to try to give you the same address each time if someone so chooses to implement a policy like that (I don't run DHCP servers so I don't know what sorts of policies are typically available).

All you can really do on the client end is force expiration and renewal of your DHCP lease.  That offers no control on what address gets assigned to that lease.

What kind of ISP do you have (cable, DSL, ...) and where is the DHCP server?  For example, some modems are both a modem and a router, so the modem is the DHCP server for your local private address space (192.168.*.* or the like), and in that case the DHCP address between the ISP head end and your end stops at the modem/router.  In other cases, where you have a pure modem, the ISP head end DHCP address shows all the way through to your computer.  (Does your modem allow multiple systems to connect through a dumb switch?  If so, then it's likely got router behavior in it.)

Followup: I was still bugged by the difference you observed between Vista/Win7 and XP/LINUX.

Turns out the DHCPDISCOVER message allows a client to request its last known IP address.  The DHCP server may or may not grant that request.  Perhaps from Vista on this behavior was added to Windows, though I don't know this to be the case for certain.

http://en.wikipedia.org/wiki/Dynamic_Host_Configuration_Protocol

The bottom line remains: DHCP gives you no way to force an address change, and never has.  The fact that you got that behavior in some cases is nothing more than a side effect of multiple client and server implementation choices.

Jim