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  • Windows Std 2003 DHCP behavior...

    First of all, I do want to apologize if my question is inapropriate for this forum.


    I have Windows 2003 Std with DHCP installed (10.x.x.x.). What will happend with W2K3 DHCP if I install Linux SuSE 10.2 DHCP service (192.168.x.x) and plug it on the same switch?

    Can't create a lab to test behaviors. I know that in some cases W2K3 DHCP is stopped automatically if he recognizes another DHCP on the network (for example NT 4.0)...

  • #2
    Re: Windows Std 2003 DHCP behavior...

    Originally posted by kojo1984 View Post
    First of all, I do want to apologize if my question is inapropriate for this forum.
    No need to apologize. I'm friendly. An AC/DC fan - we will become good friends.

    Originally posted by kojo1984 View Post
    I have Windows 2003 Std with DHCP installed (10.x.x.x.). What will happend with W2K3 DHCP if I install Linux SuSE 10.2 DHCP service (192.168.x.x) and plug it on the same switch?
    Congratulations. You will have two DHCP servers on the network. Nothing bad will happen unlness the DHCP servers have overlapping scopes. So don't overlap scopes. On the Win2k3 side, set the DHCP server properties to make 3 ping attempts before handing out a TCP/IP lease configuration to detect BAD_ADDRESSes

    Originally posted by kojo1984 View Post
    Can't create a lab to test behaviors. I know that in some cases W2K3 DHCP is stopped automatically if he recognizes another DHCP on the network (for example NT 4.0)...
    Never heard of that behavior before, however, Win2k and Win2k3 DHCP servers need to be authorized if they are AD integrated.
    VCDX3 #34, VCDX4, VCDX5, VCAP4-DCA #14, VCAP4-DCD #35, VCAP5-DCD, VCPx4, vEXPERTx4, MCSEx3, MCSAx2, MCP, CCAx2, A+
    boche.net - VMware Virtualization Evangelist
    My advice has no warranties. Follow at your own risk.

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    • #3
      Re: Windows Std 2003 DHCP behavior...

      If the two DHCP servers are plugged into the same switch, (I'm assuming it's a pure switch, operating at the physical layer, and therefore doesn't care about IP address) how will you decide which clients pick up a 192 address and which pick up a 10 address? As far as I can tell it will be completely random; the first server to respond will decide which address a client gets; which may mean he can't connect to required resources like Domain Controllers.


      Tom
      For my own and your protection, I do not provide support by private message under any circumstances. All such messages will be deleted and ignored.

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      • #4
        Re: Windows Std 2003 DHCP behavior...

        Originally posted by Stonelaughter View Post
        If the two DHCP servers are plugged into the same switch, (I'm assuming it's a pure switch, operating at the physical layer, and therefore doesn't care about IP address) how will you decide which clients pick up a 192 address and which pick up a 10 address? As far as I can tell it will be completely random; the first server to respond will decide which address a client gets; which may mean he can't connect to required resources like Domain Controllers.
        There will be reservations for PC which should have 192.168.x.x. The problem is they are scatered over 3 floors and I don't want to jum all over the building . Minor changes on IP addresses could be done over DHCP... I will plug out W2K3 DHCP, if necesary, until SuSE DHCP clients get their addresses...
        Last edited by kojo1984; 19th April 2007, 07:23.

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        • #5
          Re: Windows Std 2003 DHCP behavior...

          Windows 2003 definately will not start if it recognizes an overlapping DHCP server - I have had issues in a test environment at home, where my ADSL router was picked up by 2003 Server, so it wouldn't start, and another time where a 2000 Server DHCP was running - in that case stopping the DHCP service on the 2000 machine didn't even work - i ended up physically unplugging the machine.

          In either case the Event logs will show a failure of MS DHCP to start due to a conflicting DHCP server on the network.

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          • #6
            Re: Windows Std 2003 DHCP behavior...

            Never heard of that behavior before, however, Win2k and Win2k3 DHCP servers need to be authorized if they are AD integrated.
            I've had W2K3 DC with DHCP activated and running properly, but after changing ADSL router, it's DHCP was left running by mistake. Clients were no longer in 192.168.0.x pool. They had an 192.168.1.x addresses. W2K3 DHCP was deactivated. I' ve also heard that NT 4.0 is causing the same problem... i will look for it...
            Last edited by biggles77; 19th April 2007, 12:29. Reason: Fix quote syntax

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            • #7
              Re: Windows Std 2003 DHCP behavior...

              Originally posted by camshere View Post
              Windows 2003 definately will not start if it recognizes an overlapping DHCP server - I have had issues in a test environment at home, where my ADSL router was picked up by 2003 Server, so it wouldn't start, and another time where a 2000 Server DHCP was running - in that case stopping the DHCP service on the 2000 machine didn't even work - i ended up physically unplugging the machine.

              In either case the Event logs will show a failure of MS DHCP to start due to a conflicting DHCP server on the network.
              I do agree.... But I've missundstood DHCP behavior with NT 4.0 DHCP (when combinated with DHCP W2K3 duplicated leases of IPs can and will occure)... My bad...

              If your network uses Windows 2000 or Windows Server 2003, only include legitimate DHCP servers in Active Directory. This way, any unauthorized DHCP server that attempts to access your network will be denied.... It should be like this...
              Last edited by kojo1984; 19th April 2007, 10:19.

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              • #8
                Re: Windows Std 2003 DHCP behavior...

                Use a managed switch so you can VLAN it and keep the different subnets separated.
                1 1 was a racehorse.
                2 2 was 1 2.
                1 1 1 1 race 1 day,
                2 2 1 1 2

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                • #9
                  Re: Windows Std 2003 DHCP behavior...

                  Originally posted by biggles77 View Post
                  Use a managed switch so you can VLAN it and keep the different subnets separated.
                  Done that today... I have ordered Cisco Catalyst 2960G-48TC... I think it's a good one...

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                  • #10
                    Re: Windows Std 2003 DHCP behavior...

                    Originally posted by camshere View Post
                    Windows 2003 definately will not start if it recognizes an overlapping DHCP server - I have had issues in a test environment at home, where my ADSL router was picked up by 2003 Server, so it wouldn't start, and another time where a 2000 Server DHCP was running - in that case stopping the DHCP service on the 2000 machine didn't even work - i ended up physically unplugging the machine.

                    In either case the Event logs will show a failure of MS DHCP to start due to a conflicting DHCP server on the network.
                    This is slightly misleading.
                    See my post here for an explanation http://forums.petri.com/showthread.php?t=15288&goto#5

                    kojo1984, I agree with Biggles77, VLAN is the way to go.
                    Regards,
                    Jeremy

                    Network Consultant/Engineer
                    Baltimore - Washington area and beyond
                    www.gma-cpa.com

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