Windows 2003 retains IP address across reboots...

Hi,

We've noticed that Windows 2003 (and we think Windows XP) seems to
retain it's IP address between boots, and it does not appear to issue a
DHCP request (immediately) after being rebooted. I've been told that
this is a way to make booting in XP and 2003 look faster, with the
thinking that there was a likelihood that the machine's IP address on
the network wouldn't have changed anyway.

The problem is that if I shut down a machine (Machine A), and while that
machine is down, another machine (Machine B) acquires the IP address
that Machine A is 'retaining', when I bring Machine A up, I almost
immediately get an IP address conflict (since both Machine B and Machine
A are then trying to use the same IP address).

Is there a way to (possibly) get Windows 2003 to clear it's IP address
when it shuts down? Or, to maybe force Windows to issue a DHCP request
immediately upon rebooting?

I've been told that there is a way to do this, but haven't been able to
find it yet.

Any other workarounds and or suggestions for this problem?

Thanks in advance,
Jim

This is expected behavior. DHCP has a least time setting defined (by default
about 7 days) and within this time it will record who it leased IP to.
Computer will retain IP for these leased time even if e.g. DHCP goes down or
you shut down your computer.

DHCP should not give out this IP address to any other computer within this
lease time. (Do you have only one DHCP on your server or more?). What you
can do is shorten DHCP lease time to e.g. 1 day or 8 hours or etc... Another
thing that you can do is deploy shutdown script that will contain

ipconfig /release

This way computer will release IP before it is shut down and will request
new IP from DHCP when it starts. It is still possible that it will get same
IP after reboot (DHCP tend to issue same IPs to same computers whenever
possible)...

You can view DHCP lease time of you e.g. run ipcofnig /all on your server.

Mike

"ohaya" <(E-Mail Removed)> wrote in message news:(E-Mail Removed)...
> Hi,
>
> We've noticed that Windows 2003 (and we think Windows XP) seems to
> retain it's IP address between boots, and it does not appear to issue a
> DHCP request (immediately) after being rebooted. I've been told that
> this is a way to make booting in XP and 2003 look faster, with the
> thinking that there was a likelihood that the machine's IP address on
> the network wouldn't have changed anyway.
>
> The problem is that if I shut down a machine (Machine A), and while that
> machine is down, another machine (Machine B) acquires the IP address
> that Machine A is 'retaining', when I bring Machine A up, I almost
> immediately get an IP address conflict (since both Machine B and Machine
> A are then trying to use the same IP address).
>
> Is there a way to (possibly) get Windows 2003 to clear it's IP address
> when it shuts down? Or, to maybe force Windows to issue a DHCP request
> immediately upon rebooting?
>
> I've been told that there is a way to do this, but haven't been able to
> find it yet.
>
> Any other workarounds and or suggestions for this problem?
>
> Thanks in advance,
> Jim

Miha Pihler wrote:
>
> This is expected behavior. DHCP has a least time setting defined (by default
> about 7 days) and within this time it will record who it leased IP to.
> Computer will retain IP for these leased time even if e.g. DHCP goes down or
> you shut down your computer.
>
> DHCP should not give out this IP address to any other computer within this
> lease time. (Do you have only one DHCP on your server or more?). What you
> can do is shorten DHCP lease time to e.g. 1 day or 8 hours or etc... Another
> thing that you can do is deploy shutdown script that will contain
>
> ipconfig /release
>
> This way computer will release IP before it is shut down and will request
> new IP from DHCP when it starts. It is still possible that it will get same
> IP after reboot (DHCP tend to issue same IPs to same computers whenever
> possible)...
>
> You can view DHCP lease time of you e.g. run ipcofnig /all on your server.
>


Mike,

Thanks for the 'hint' re. shutdown scripts. I've used GPEDIT.MSC to add
a shutdown script doing the 'ipconfig /release', and that seems to do
the job, and I'll test in our 'real' test environment today.

We have a bit unusual network configuration, where the servers are
configured to "obtain IP address" and we have MAC reservation set up on
our DHCP server to serve IP addresses to all of our servers.

Without the 'release' in the shutdown script, the Win2K3 machines not
releasing their leases was causing a problem if a particular machine was
installed and tested with a fixed IP (during test) and then later set to
"obtain IP address" (in production).

This (IP conflicts) had not been a problem with Win2K Server machines
that we were deploying, and until we started trying Win2K3 (we just
started testing deploying Win2K3), so it appears that even though it
might be "expected behavior", something changed between Win2K Server and
Win2K3 Server?

Jim

<snip>

> This (IP conflicts) had not been a problem with Win2K Server machines
> that we were deploying, and until we started trying Win2K3 (we just
> started testing deploying Win2K3), so it appears that even though it
> might be "expected behavior", something changed between Win2K Server and
> Win2K3 Server?

I am not sure what changed. It could be that Windows 2000 checked in with
DHCP after reboot to see if the IP was still available even if the lease
time did not expire.

Mike

<snip>

Miha Pihler wrote:
>
> <snip>
>
> > This (IP conflicts) had not been a problem with Win2K Server machines
> > that we were deploying, and until we started trying Win2K3 (we just
> > started testing deploying Win2K3), so it appears that even though it
> > might be "expected behavior", something changed between Win2K Server and
> > Win2K3 Server?
>
> I am not sure what changed. It could be that Windows 2000 checked in with
> DHCP after reboot to see if the IP was still available even if the lease
> time did not expire.
>
> Mike


Mike,

That looks EXACTLY like what changed..., at least from my testing.

Again, thanks for your help!

Jim