Force workstation to use a specific DHCP server?

Hello!

Does anyone know of a way to force a workstation to use a specific DHCP
server? I just ran into a situation where a Windows Server 2003 domain has
DHCP on the server, and the Nortel BCM telephone system also has DHCP
enabled.

One workstation keeps getting its IP information from the Nortel DHCP server
rather than the 2003 server, and I want to force the workstations to get
their IPs from the 2003 server.

Yes, I know the real fix is to kill DHCP on the Nortel system, and we are
going to contact their tech support on Monday to find out why it is enabled
in the first place.

I am looking for a registry setting to force it in case the Nortel folks
ever turn their DHCP back on.

Thank you!

Gregg Hill

Gregg Hill <greggmhill at please do not spam me at yahoo dot com> wrote:
> Hello!
>
> Does anyone know of a way to force a workstation to use a specific
> DHCP server? I just ran into a situation where a Windows Server 2003
> domain has DHCP on the server, and the Nortel BCM telephone system
> also has DHCP enabled.
>
> One workstation keeps getting its IP information from the Nortel DHCP
> server rather than the 2003 server, and I want to force the
> workstations to get their IPs from the 2003 server.
>
> Yes, I know the real fix is to kill DHCP on the Nortel system, and we
> are going to contact their tech support on Monday to find out why it
> is enabled in the first place.
>
> I am looking for a registry setting to force it in case the Nortel
> folks ever turn their DHCP back on.
>
> Thank you!
>
> Gregg Hill

Hi, Gregg - no, there's no way to do that. DHCP is first come, first serve
if your phones & workstations are all on the same network. You're correct in
that the Nortel should not have DHCP enabled. Note also that this newsgroup
is for wireless issues - your question best belongs in
microsoft.public.windows.server.networking.

Lanwench,

I was afraid of that! I chose this newsgroup as a toss-up between it not
really being a server issue, and as close as I could get to just a
networking concern. It was the only public.windows.networking one I found.
Thank you for the suggestion of the other group.

Thank you!

Gregg Hill


"Lanwench [MVP - Exchange]"
<(E-Mail Removed) hoo.com> wrote in message
news:%(E-Mail Removed)...
> Gregg Hill <greggmhill at please do not spam me at yahoo dot com> wrote:
>> Hello!
>>
>> Does anyone know of a way to force a workstation to use a specific
>> DHCP server? I just ran into a situation where a Windows Server 2003
>> domain has DHCP on the server, and the Nortel BCM telephone system
>> also has DHCP enabled.
>>
>> One workstation keeps getting its IP information from the Nortel DHCP
>> server rather than the 2003 server, and I want to force the
>> workstations to get their IPs from the 2003 server.
>>
>> Yes, I know the real fix is to kill DHCP on the Nortel system, and we
>> are going to contact their tech support on Monday to find out why it
>> is enabled in the first place.
>>
>> I am looking for a registry setting to force it in case the Nortel
>> folks ever turn their DHCP back on.
>>
>> Thank you!
>>
>> Gregg Hill
>
> Hi, Gregg - no, there's no way to do that. DHCP is first come, first serve
> if your phones & workstations are all on the same network. You're correct
> in that the Nortel should not have DHCP enabled. Note also that this
> newsgroup is for wireless issues - your question best belongs in
> microsoft.public.windows.server.networking.
>
>
>

There is another option: filtering DHCP replies based on MAC address
of the server or some data in the reply, on NDIS level.
But this kind of solution is an overkill in your situation.

--PA

Gregg Hill wrote:
> Lanwench,
>
> I was afraid of that! I chose this newsgroup as a toss-up between it not
> really being a server issue, and as close as I could get to just a
> networking concern. It was the only public.windows.networking one I found.
> Thank you for the suggestion of the other group.
>
> Thank you!
>
> Gregg Hill
>
>
> "Lanwench [MVP - Exchange]"
> <(E-Mail Removed) hoo.com> wrote in message
> news:%(E-Mail Removed)...
>> Gregg Hill <greggmhill at please do not spam me at yahoo dot com> wrote:
>>> Hello!
>>>
>>> Does anyone know of a way to force a workstation to use a specific
>>> DHCP server? I just ran into a situation where a Windows Server 2003
>>> domain has DHCP on the server, and the Nortel BCM telephone system
>>> also has DHCP enabled.
>>>
>>> One workstation keeps getting its IP information from the Nortel DHCP
>>> server rather than the 2003 server, and I want to force the
>>> workstations to get their IPs from the 2003 server.
>>>
>>> Yes, I know the real fix is to kill DHCP on the Nortel system, and we
>>> are going to contact their tech support on Monday to find out why it
>>> is enabled in the first place.
>>>
>>> I am looking for a registry setting to force it in case the Nortel
>>> folks ever turn their DHCP back on.
>>>
>>> Thank you!
>>>
>>> Gregg Hill
>> Hi, Gregg - no, there's no way to do that. DHCP is first come, first serve
>> if your phones & workstations are all on the same network. You're correct
>> in that the Nortel should not have DHCP enabled. Note also that this
>> newsgroup is for wireless issues - your question best belongs in
>> microsoft.public.windows.server.networking.
>>
>>
>>
>
>

Its only an overkill if the Nortel phone people end up telling us that they
need DHCP enabled! In which case I will methodically pound my head on my
desk until unconsciousness relieves me of my misery.

How would I do what you mentioned, just out of curiosity?

Gregg Hill


"Pavel A." <(E-Mail Removed)> wrote in message
news:%(E-Mail Removed)...
> There is another option: filtering DHCP replies based on MAC address
> of the server or some data in the reply, on NDIS level.
> But this kind of solution is an overkill in your situation.
>
> --PA
>
> Gregg Hill wrote:
>> Lanwench,
>>
>> I was afraid of that! I chose this newsgroup as a toss-up between it not
>> really being a server issue, and as close as I could get to just a
>> networking concern. It was the only public.windows.networking one I
>> found. Thank you for the suggestion of the other group.
>>
>> Thank you!
>>
>> Gregg Hill
>>
>>
>> "Lanwench [MVP - Exchange]"
>> <(E-Mail Removed) hoo.com> wrote in
>> message news:%(E-Mail Removed)...
>>> Gregg Hill <greggmhill at please do not spam me at yahoo dot com> wrote:
>>>> Hello!
>>>>
>>>> Does anyone know of a way to force a workstation to use a specific
>>>> DHCP server? I just ran into a situation where a Windows Server 2003
>>>> domain has DHCP on the server, and the Nortel BCM telephone system
>>>> also has DHCP enabled.
>>>>
>>>> One workstation keeps getting its IP information from the Nortel DHCP
>>>> server rather than the 2003 server, and I want to force the
>>>> workstations to get their IPs from the 2003 server.
>>>>
>>>> Yes, I know the real fix is to kill DHCP on the Nortel system, and we
>>>> are going to contact their tech support on Monday to find out why it
>>>> is enabled in the first place.
>>>>
>>>> I am looking for a registry setting to force it in case the Nortel
>>>> folks ever turn their DHCP back on.
>>>>
>>>> Thank you!
>>>>
>>>> Gregg Hill
>>> Hi, Gregg - no, there's no way to do that. DHCP is first come, first
>>> serve if your phones & workstations are all on the same network. You're
>>> correct in that the Nortel should not have DHCP enabled. Note also that
>>> this newsgroup is for wireless issues - your question best belongs in
>>> microsoft.public.windows.server.networking.
>>>
>>>
>>>
>>

Gregg Hill wrote:
> Its only an overkill if the Nortel phone people end up telling us that they
> need DHCP enabled! In which case I will methodically pound my head on my
> desk until unconsciousness relieves me of my misery.
>
> How would I do what you mentioned, just out of curiosity?

Ok... First of all, see (with a sniffer) how you can distinguish dhcp
replies from yours and their servers.
For example, their may have certain IP address or MAC address, or
certain values in features field.

Next, try to tweak your firewall to block their
server replies, based on the above data.

Finally, if this fails... ask in
microsoft.public.win32.programmer.networks ,
how to make a NDIS filter driver.

Regards,
--PA


> "Pavel A." <(E-Mail Removed)> wrote in message
> news:%(E-Mail Removed)...
>> There is another option: filtering DHCP replies based on MAC address
>> of the server or some data in the reply, on NDIS level.
>> But this kind of solution is an overkill in your situation.
>>
>> --PA
>>
>> Gregg Hill wrote:
>>> Lanwench,
>>>
>>> I was afraid of that! I chose this newsgroup as a toss-up between it not
>>> really being a server issue, and as close as I could get to just a
>>> networking concern. It was the only public.windows.networking one I
>>> found. Thank you for the suggestion of the other group.
>>>
>>> Thank you!
>>>
>>> Gregg Hill
>>>
>>>
>>> "Lanwench [MVP - Exchange]"
>>> <(E-Mail Removed) hoo.com> wrote in
>>> message news:%(E-Mail Removed)...
>>>> Gregg Hill <greggmhill at please do not spam me at yahoo dot com> wrote:
>>>>> Hello!
>>>>>
>>>>> Does anyone know of a way to force a workstation to use a specific
>>>>> DHCP server? I just ran into a situation where a Windows Server 2003
>>>>> domain has DHCP on the server, and the Nortel BCM telephone system
>>>>> also has DHCP enabled.
>>>>>
>>>>> One workstation keeps getting its IP information from the Nortel DHCP
>>>>> server rather than the 2003 server, and I want to force the
>>>>> workstations to get their IPs from the 2003 server.
>>>>>
>>>>> Yes, I know the real fix is to kill DHCP on the Nortel system, and we
>>>>> are going to contact their tech support on Monday to find out why it
>>>>> is enabled in the first place.
>>>>>
>>>>> I am looking for a registry setting to force it in case the Nortel
>>>>> folks ever turn their DHCP back on.
>>>>>
>>>>> Thank you!
>>>>>
>>>>> Gregg Hill
>>>> Hi, Gregg - no, there's no way to do that. DHCP is first come, first
>>>> serve if your phones & workstations are all on the same network. You're
>>>> correct in that the Nortel should not have DHCP enabled. Note also that
>>>> this newsgroup is for wireless issues - your question best belongs in
>>>> microsoft.public.windows.server.networking.

Yes, they are on the same subnet, not at my doing. And yes, it is confusing,
as currently one workstation out of four gets its IP from the damn phone
system!

This client is new and I just found out the Nortel system was handing out
DHCP as well as the server. We have a call in to the Nortel folks to find
out WHY they have DHCP enabled. The phones themselves do not appear to be IP
phones, at least not at first glance (same type of connecting cable to the
wall as a POTS line).

Gregg Hill


"smlunatick" <(E-Mail Removed)> wrote in message
news:e9fc1ed1-04db-4b3e-bfbf-(E-Mail Removed)...
On Aug 4, 6:54 pm, "Gregg Hill" <greggmhill at please do not spam me
at yahoo dot com> wrote:
> Its only an overkill if the Nortel phone people end up telling us that
> they
> need DHCP enabled! In which case I will methodically pound my head on my
> desk until unconsciousness relieves me of my misery.
>
> How would I do what you mentioned, just out of curiosity?
>
> Gregg Hill
>
> "Pavel A." <pave...@NOfastmailNO.fm> wrote in message
>
> news:%(E-Mail Removed)...
>
> > There is another option: filtering DHCP replies based on MAC address
> > of the server or some data in the reply, on NDIS level.
> > But this kind of solution is an overkill in your situation.
>
> > --PA
>
> > Gregg Hill wrote:
> >> Lanwench,
>
> >> I was afraid of that! I chose this newsgroup as a toss-up between it
> >> not
> >> really being a server issue, and as close as I could get to just a
> >> networking concern. It was the only public.windows.networking one I
> >> found. Thank you for the suggestion of the other group.
>
> >> Thank you!
>
> >> Gregg Hill
>
> >> "Lanwench [MVP - Exchange]"
> >> <lanwe...@heybuddy.donotsendme.unsolicitedmailatya hoo.com> wrote in
> >> messagenews:%(E-Mail Removed) l...
> >>> Gregg Hill <greggmhill at please do not spam me at yahoo dot com>
> >>> wrote:
> >>>> Hello!
>
> >>>> Does anyone know of a way to force a workstation to use a specific
> >>>> DHCP server? I just ran into a situation where a Windows Server 2003
> >>>> domain has DHCP on the server, and the Nortel BCM telephone system
> >>>> also has DHCP enabled.
>
> >>>> One workstation keeps getting its IP information from the Nortel DHCP
> >>>> server rather than the 2003 server, and I want to force the
> >>>> workstations to get their IPs from the 2003 server.
>
> >>>> Yes, I know the real fix is to kill DHCP on the Nortel system, and we
> >>>> are going to contact their tech support on Monday to find out why it
> >>>> is enabled in the first place.
>
> >>>> I am looking for a registry setting to force it in case the Nortel
> >>>> folks ever turn their DHCP back on.
>
> >>>> Thank you!
>
> >>>> Gregg Hill
> >>> Hi, Gregg - no, there's no way to do that. DHCP is first come, first
> >>> serve if your phones & workstations are all on the same network.
> >>> You're
> >>> correct in that the Nortel should not have DHCP enabled. Note also
> >>> that
> >>> this newsgroup is for wireless issues - your question best belongs in
> >>> microsoft.public.windows.server.networking.

Are the "two" DHCP "service" on the same network sub-net? It can be
confusing if the two DHCP servers gives out IPs on the same network.
You might have to re-consider your DHCP server IP pool (aka range) so
as to be able to assign IPs for the phones and PCs from one DHCP
server.

Holy Zimbabwe!

You were right when you said it was overkill!

There is no firewall between the two DHCP servers. Their Nortel system has a
network cable on the LAN switch, hence the competition with the Windows DHCP
server. For all I know, it is just for them to get remote access to the
phone system. I'll find out when they respond.

Gregg Hill



"Pavel A." <(E-Mail Removed)> wrote in message
news:%(E-Mail Removed)...
> Gregg Hill wrote:
>> Its only an overkill if the Nortel phone people end up telling us that
>> they need DHCP enabled! In which case I will methodically pound my head
>> on my desk until unconsciousness relieves me of my misery.
>>
>> How would I do what you mentioned, just out of curiosity?
>
> Ok... First of all, see (with a sniffer) how you can distinguish dhcp
> replies from yours and their servers.
> For example, their may have certain IP address or MAC address, or
> certain values in features field.
>
> Next, try to tweak your firewall to block their
> server replies, based on the above data.
>
> Finally, if this fails... ask in
> microsoft.public.win32.programmer.networks ,
> how to make a NDIS filter driver.
>
> Regards,
> --PA
>
>
>> "Pavel A." <(E-Mail Removed)> wrote in message
>> news:%(E-Mail Removed)...
>>> There is another option: filtering DHCP replies based on MAC address
>>> of the server or some data in the reply, on NDIS level.
>>> But this kind of solution is an overkill in your situation.
>>>
>>> --PA
>>>
>>> Gregg Hill wrote:
>>>> Lanwench,
>>>>
>>>> I was afraid of that! I chose this newsgroup as a toss-up between it
>>>> not really being a server issue, and as close as I could get to just a
>>>> networking concern. It was the only public.windows.networking one I
>>>> found. Thank you for the suggestion of the other group.
>>>>
>>>> Thank you!
>>>>
>>>> Gregg Hill
>>>>
>>>>
>>>> "Lanwench [MVP - Exchange]"
>>>> <(E-Mail Removed) hoo.com> wrote in
>>>> message news:%(E-Mail Removed)...
>>>>> Gregg Hill <greggmhill at please do not spam me at yahoo dot com>
>>>>> wrote:
>>>>>> Hello!
>>>>>>
>>>>>> Does anyone know of a way to force a workstation to use a specific
>>>>>> DHCP server? I just ran into a situation where a Windows Server 2003
>>>>>> domain has DHCP on the server, and the Nortel BCM telephone system
>>>>>> also has DHCP enabled.
>>>>>>
>>>>>> One workstation keeps getting its IP information from the Nortel DHCP
>>>>>> server rather than the 2003 server, and I want to force the
>>>>>> workstations to get their IPs from the 2003 server.
>>>>>>
>>>>>> Yes, I know the real fix is to kill DHCP on the Nortel system, and we
>>>>>> are going to contact their tech support on Monday to find out why it
>>>>>> is enabled in the first place.
>>>>>>
>>>>>> I am looking for a registry setting to force it in case the Nortel
>>>>>> folks ever turn their DHCP back on.
>>>>>>
>>>>>> Thank you!
>>>>>>
>>>>>> Gregg Hill
>>>>> Hi, Gregg - no, there's no way to do that. DHCP is first come, first
>>>>> serve if your phones & workstations are all on the same network.
>>>>> You're correct in that the Nortel should not have DHCP enabled. Note
>>>>> also that this newsgroup is for wireless issues - your question best
>>>>> belongs in microsoft.public.windows.server.networking.

"Gregg Hill" <greggmhill at please do not spam me at yahoo dot com> wrote in
message news:%(E-Mail Removed)...
> Yes, they are on the same subnet, not at my doing. And yes, it is
> confusing, as currently one workstation out of four gets its IP from the
> damn phone system!

The answer here is,..."You just can't do that",...period.

DHCP is "first-come-first-serve". The DHCP Server that answers the query
ahead of the other one "wins" and that is the one used. There is no
reasonably decent, do-able, acceptable way to make clients get an IP Config
from a specific DHCP Server as far as I am concerned.

Either put the phones on their own subnet so they can use their own DHCP
Server or the phones will have to get the IP Config from the regular LAN's
Windows based DHCP Server. Anything other than that is just simply a
disaster.

--
Phillip Windell
www.wandtv.com

The views expressed, are my own and not those of my employer, or Microsoft,
or anyone else associated with me, including my cats.
-----------------------------------------------------

Hello, everyone!

The Nortel tech finally called back and confirmed what I suspected, i.e.,
there was no need for the Nortel system to have DHCP enabled. He will come
out tomorrow to turn it off. He has no idea why it was ever enabled.

Gregg Hill






"Phillip Windell" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> "Gregg Hill" <greggmhill at please do not spam me at yahoo dot com> wrote
> in message news:%(E-Mail Removed)...
>> Yes, they are on the same subnet, not at my doing. And yes, it is
>> confusing, as currently one workstation out of four gets its IP from the
>> damn phone system!
>
> The answer here is,..."You just can't do that",...period.
>
> DHCP is "first-come-first-serve". The DHCP Server that answers the query
> ahead of the other one "wins" and that is the one used. There is no
> reasonably decent, do-able, acceptable way to make clients get an IP
> Config from a specific DHCP Server as far as I am concerned.
>
> Either put the phones on their own subnet so they can use their own DHCP
> Server or the phones will have to get the IP Config from the regular LAN's
> Windows based DHCP Server. Anything other than that is just simply a
> disaster.
>
> --
> Phillip Windell
> www.wandtv.com
>
> The views expressed, are my own and not those of my employer, or
> Microsoft,
> or anyone else associated with me, including my cats.
> -----------------------------------------------------
>
>