Hi On our network every computer is assigned one IP address. With windows 7, when someone goes from their wired connection and switches to wireless, windows will not accept the address. Now I realize that you can't have one IP on two devices at once, but this is when one is turned off and the other is on. Even by using IP config to release the address on one and try to connect with the other it won't get the IP. We can see on the server log the computer repeatedly asking for the IP. Now if I release the IP of one, reboot with the other connect, it works fine. I know one solution would be to assign each computer 2 IPs, but this isn't practical. We don't have this issue with our XP machines. Any help would be appreciated. Thanks!

Hello Thumper81, Generally when you release and renew, DHCP will offer you the same address IF you renew from the same adapter. However, since you are switching from one adapter to another and the adapter's MAC addresses are different, DHCP will likely NOT grant you the same address if you release and renew in a relatively short time. I suppose that you could set one adapter as static and the other dynamic the have DHCP assigh the same address to the adapter that's dynamic using a MAC address table. So for example, if you LAN adapter is set static to 192.168.0.10 and the WLAN adapter is dynamic, but through DHCP you assign 192.168.0.10 via the MAC address filter, then in theory you should get the same address when you toggle back and forth. I say in theory because I have never done it before but it sounds like it would work. I don't think this is a very elegant solution but maybe someone else can shed some light and provide some additional ideas. BTW, wht is it that you are tying to accomplisg?Miguel Fra / Falcon ITS Computer & Network Support, Miami, FL Visit our Knowledgebase Sharepoint Site

The DHCP isn't the problem. We can see it requesting the IP address and the DHCP sending the IP on the server log repeatedly. The reason why we do this is to only allow work computers on the network as to not introduce any new problems. When the IP is released by the first adapter, it should no longer, as far as the the client is concerned, be associated with that adapter. As stated, XP and Linux clients can switch between the two without any issue. It's only the new Windows 7 machines that are causing this headache. Giving out an IP per adapter isn't practical and can lead to more problems. The issue isn't in our server, it's some feature in Win7 that won't fully release the IP associated with the disabled adapter. Thanks

I think this is more hardware related than software. If your DHCP server is acting correctly he should not permanently give one IP-address to two hardware addresses. Maybe you circumvented this problem by spoofing the hardware address of one adapter to be the same as the one of the other adapter and that is not possible or done now. How do you switch off the wired connection? Just pull the plug? In that case the DHCP server will not release the same IP address to another hardware address before the lease time is expired. And if it does it would be against the RFC rules for DHCP. What if you assign each IP-address on the Win 7 computer manually, thus eliminating DHCP.Wolfgang

WolfP Our server sees either of the MAC addresses and associates it with a single IP. I've even disable one of the adapters and switched over and the client still will not accept the given IP from DHCP. XP and Linux clients can do this no problem, it's just win7 clients that are the issue. However, if you disconnect one, connect the other, and reboot there is no problem. It's almost as if win7 is keeping the IP in memory somewhere even after the adapter has been disconnected and disabled. As for the static option, it would be a solution for our desktops, but not our laptop clients that take their machines home with them. Thanks!

Thumper81 wrote: WolfP   Our server sees either of the MAC addresses and associates it with a single IP.  I've even disable one of the adapters and switched over and the client still will not accept the given IP from DHCP.  XP and Linux clients can do this no problem, it's just win7 clients that are the issue.  However, if you disconnect one, connect the other, and reboot there is no problem.  It's almost as if win7 is keeping the IP in memory somewhere even after the adapter has been disconnected and disabled.  As for the static option, it would be a solution for our desktops, but not our laptop clients that take their machines home with them.    Thanks! For a quick solution I'd take the 2 addresses route. I don't know which private address range you use, but e.g. in the 10.0.0.0/255.0.0.0 net there should be enough addresses available. ( We have her each PC with two NICs bound to two different nets; network addresses for both NICs are identical except of one number e.g. 10.1.x.y and 10.2.x.y - that way it is easy to see, which addresses belong to the same machine). HTH Wolfgang