Force workstation to use a specific DHCP server?

Discussion in 'Wireless Networks' started by Gregg Hill, Aug 3, 2008.

  1. Gregg Hill

    Gregg Hill Guest

    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, Aug 3, 2008
    #1
    1. Advertisements

  2. 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 [MVP - Exchange], Aug 3, 2008
    #2
    1. Advertisements

  3. Gregg Hill

    Gregg Hill Guest

    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]"
     
    Gregg Hill, Aug 3, 2008
    #3
  4. Gregg Hill

    Pavel A. Guest

    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

     
    Pavel A., Aug 3, 2008
    #4
  5. Gregg Hill

    Gregg Hill Guest

    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


     
    Gregg Hill, Aug 4, 2008
    #5
  6. Gregg Hill

    Pavel A. Guest

    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., Aug 4, 2008
    #6
  7. Gregg Hill

    Gregg Hill Guest

    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


    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.
     
    Gregg Hill, Aug 5, 2008
    #7
  8. Gregg Hill

    Gregg Hill Guest

    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



     
    Gregg Hill, Aug 5, 2008
    #8
  9. 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.
    -----------------------------------------------------
     
    Phillip Windell, Aug 5, 2008
    #9
  10. Gregg Hill

    Gregg Hill Guest

    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
     
    Gregg Hill, Aug 6, 2008
    #10
  11. Ah! Ok,..very good.

    --
    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.
    -----------------------------------------------------

     
    Phillip Windell, Aug 6, 2008
    #11
    1. Advertisements

Ask a Question

Want to reply to this thread or ask your own question?

You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.