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

Thanks for the clarification!  I can see how it could be read either way...I guess my instinct is to assume sarcasm in forums, since flaming and sarcasm seem so prevalent on open forums...which is sad!

On the topic of security, cookies and addresses are very different animals.  Clearing cookies is to keep web sites from detecting that you are a returning user regardless of IP address, as a UID in the cookie is all that is needed to find a returning user.  Addresses don't even matter.  For that kind of privacy, addresses are not even very useful, as they change and are shared often enough, and routers / firewalls that change addresses make them useless for tracking users.  (When I'm behind my corporate firewall browsing the web, a few hundred thousand fellow workers all probably map to the same handful of external addresses; not much info to mine from that!)

As far as attack security, I don't think DHCP does much to help.  Any worthy attacker isn't going to focus on one fixed address, better to just spray the whole subnet that has known vulnerabilities to find all the candidates.  Most attacks that I'm aware of that propagate by network port vulnerabilities (as opposed to social engineering like email payloads and the like) do exactly this subnet blasting.  The reality is that DHCP isn't going to give you a unique address every time, at some level it has to cycle through the range of addresses in the subnet that your ISP has assigned to your area (assuming it's regional).  That could be a pretty small number of candidates before you repeat, and hackers just spray to everything in a subnet to see what hits a target.  Your 'known address becomes unknown" scenario is really "known address becomes unknown within the same subnet", where the subnet could be a few hundred to a few thousand addresses.  That's maybe a few minutes of scan time for a network probe tool.  That's so easy that it isn't even worth bothering fixing on one address, the hacker just gets a probe hit and then throws all known attacks at that address right away.  Dynamic addresses are no help at all for this.

Since you have no router/firewall, those attacks are going right up against the software firewall on your OS.  All you have to do is have a net monitor watch the non-firewalled traffic on your incoming ISP signal to see that going on all the time.  You could play with a net scan tool like Wireshark and probably see a steady stream of probes coming in, which are fortunately blocked by firewalls and up to date OS patches.

I'll fully agree with you on one thing: nowhere did I come across any info that discusses the behavior change between XP and Vista or shows where the DHCP address is stored for requested reuse.

Jim

@tony1967

Hi,

You should open a command prompt and type "arp -a" on your seven machine.

Then, come back and tell the results to us.

Eventually, clear the arp cache to be sure that it can't be transfered while the DHCPdiscover process.

MCP | MCTS on Win2008 Networking Infrastructure | Cisco Certified Network Associate

I'm totally lost here.

by tony1967:

"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."

Obviously you know a bit about networking.  But what I'm confused about is the 'why' part.  The DHCP is just your near side address; your router's far side is your IP address to your house, regardless of what you set your nearside dhcp to be.  As you don't use a router, that's sort of useless, I guess. 

I run a small network at home, and a very, very large network at work.  At work we use static, easier to track who's doing what.  But at home I use dhcp through a hybrid linksys router.  I've assigned the 192.168.x.x to my main rig (at the router) and done the same for my wife's vista machine; even though it's dhcp, I prefer to have it something more creative than 192.168.1.1.  Bit security conscious.

The 'why' obviously comes to mind, but you've already stated that's not the issue. 

I've googled it a bit, can't seem to find an answer to your particular question.  I know you can set it to a particular address using the netsh command, but from what I gather you'd rather have windows change it for you randomly.

I'll see what else I can find.

thanks,

v

M.V.P. - Desktop Experience | M.C.S.A. | M.C.P. - MS Server 2k3, Network Architecture

same problem!!!

 easy to get new ip on xp but windows 7,this really upset me .

ip not completely release i think,"cache" hide somewhere.

any solution, plz let me know advance thx.