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  • Switch DHCP to different server - clients fail

    Hello,

    I am attempting to transfer the DHCP role from an older Domain Controller (DC1), that needs to be taken out of our server rotation, to a newer DC (DC2). I backed up successfully and installed/imported successfully on to DC2.
    However, when I stopped the DHCP service on DC1 and started it on DC2, I ran in to a problem. The first client I booted up, and logged in to, had an IP way outside any reasonable scope. It did not just 0-out (0.0.0.0), it seemed to go outside our forest to obtain an IP.
    Am I missing a setting somewhere that tells clients where to look for DHCP services? The change from DC1 to DC2 means that the DHCP service is residing on a server with a different name and IP.

    Unfortunately, testing is rather difficult as DC1 is our production DHCP server. Any ideas would be very helpful, I just don't know when I'll get a chance to test!

    Thank You

  • #2
    Re: Switch DHCP to different server - clients fail

    Hi mmX.
    Originally posted by mmX View Post
    However, when I stopped the DHCP service on DC1 and started it on DC2, I ran in to a problem. The first client I booted up, and logged in to, had an IP way outside any reasonable scope. It did not just 0-out (0.0.0.0), it seemed to go outside our forest to obtain an IP.
    Was the IP address in the 169.254.x.x range? If so then that means the client couldn't contact a DHCP server.

    Am I missing a setting somewhere that tells clients where to look for DHCP services? The change from DC1 to DC2 means that the DHCP service is residing on a server with a different name and IP.
    Clients must be in the same Broadcast Domain as the DHCP server or DHCP relay.


    Unfortunately, testing is rather difficult as DC1 is our production DHCP server. Any ideas would be very helpful, I just don't know when I'll get a chance to test!
    Where is DC2? What is the network setup? Have you check DC2 to make sure the DHCP server is running?
    Regards,
    Jeremy

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

    Comment


    • #3
      Re: Switch DHCP to different server - clients fail

      Hey Jeremy,

      Thanks for taking a look.

      The IP was in the 169.254.*.* range.
      Clients are in the broadcast range.

      DC1 is *.*.165.6, while DC2 is *.*.165.250...
      The testing problem is that fact that I don't think I can stop the DHCP service on DC1 without dropping everyone in the domain, eh?

      Comment


      • #4
        Re: Switch DHCP to different server - clients fail

        Well testing it in a live environment can hard and dangerous. But keep in mind that when you disable the DHCP service it doesn't remove the IP addresses from the clients. You'll run into trouble when clients' leases start running out.

        But, since DC1 is still running, you could put one DHCP client and DC2 on a hub or switch that doesn't connect to anything else and test it that way.

        Would you mind posting your configs.? (DHCP scope, IP address, mask, DNS, gateway, etc.)

        EDIT - have you Authorized DC2 in Active Directory?
        Last edited by JeremyW; 13th November 2006, 19:10.
        Regards,
        Jeremy

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

        Comment


        • #5
          Re: Switch DHCP to different server - clients fail

          DC2 is authorized...
          Is there an easy (easily readable) way to extract said information?

          Comment


          • #6
            Re: Switch DHCP to different server - clients fail

            How 'bout typing it?
            It shouldn't be too much info...
            ipconfig /all -> copy and paste, write scope, note anything else that is pertinent
            Regards,
            Jeremy

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

            Comment


            • #7
              Re: Switch DHCP to different server - clients fail

              Also,
              Shorten you're lease time dramaticaly to for example 1 hour.
              Wait until you're current lease time has passed over.
              Disable the old one, en enable the new one at the end of the day when the 1 hour lease is active.
              Wait for at leas one hour. then run Ipconfig /renew or reboot you're machine.

              However, 169.254.x.x means he can't contact the dhcp server.
              Make sure he's in the same broadcast domain.
              Check you're event viewers (either from client and server)

              also see:
              http://support.microsoft.com/kb/325473
              Marcel
              Technical Consultant
              Netherlands
              http://www.phetios.com
              http://blog.nessus.nl

              MCITP(EA, SA), MCSA/E 2003:Security, CCNA, SNAF, DCUCI, CCSA/E/E+ (R60), VCP4/5, NCDA, NCIE - SAN, NCIE - BR, EMCPE
              "No matter how secure, there is always the human factor."

              "Enjoy life today, tomorrow may never come."
              "If you're going through hell, keep going. ~Winston Churchill"

              Comment


              • #8
                Re: Switch DHCP to different server - clients fail

                Windows IP Configuration

                Host Name . . . . . . . . . . . . : DC1
                Primary Dns Suffix . . . . . . . : x.x.EDU
                Node Type . . . . . . . . . . . . : Hybrid
                IP Routing Enabled. . . . . . . . : No
                WINS Proxy Enabled. . . . . . . . : No
                DNS Suffix Search List. . . . . . : x.x.EDU
                x.EDU

                Ethernet adapter Local Area Connection:

                Connection-specific DNS Suffix . :
                Description . . . . . . . . . . . : AsantéFAST 10/100 PCI Rev B Adapter
                Physical Address. . . . . . . . . : 00-00-94-B7-5A-D3
                DHCP Enabled. . . . . . . . . . . : No
                IP Address. . . . . . . . . . . . : x.x.165.8
                Subnet Mask . . . . . . . . . . . : 255.255.255.0
                Default Gateway . . . . . . . . . : x.x.165.1
                x.x.165.5
                DNS Servers . . . . . . . . . . . : x.x.103.79
                x.x.103.78
                x.x.100.64
                x.x.103.75
                Primary WINS Server . . . . . . . : x.x.165.6
                Secondary WINS Server . . . . . . : x.x.165.8

                Scope: x.x.165.0 (x.x.165.0/24)

                Anything else?

                Comment


                • #9
                  Re: Switch DHCP to different server - clients fail

                  Originally posted by Dumber View Post
                  Also,
                  Shorten you're lease time dramaticaly to for example 1 hour.
                  Wait until you're current lease time has passed over.
                  Disable the old one, en enable the new one at the end of the day when the 1 hour lease is active.
                  Wait for at leas one hour. then run Ipconfig /renew or reboot you're machine.

                  However, 169.254.x.x means he can't contact the dhcp server.
                  Make sure he's in the same broadcast domain.
                  Check you're event viewers (either from client and server)

                  also see:
                  http://support.microsoft.com/kb/325473
                  Alright, so I was just probably approaching this wrong from inception. I thought I had unsuccessfully run ipconfig /renew on my test client, I could be wrong.

                  Plan of attack:
                  Reduce lease time on DC1 to incredibly short time (ex. 1 hour).
                  Wait for the end of the work day to roll around.
                  As clients shut-down all leases should be freed.
                  After all leased IPs are free, stop DHCP service on DC1.
                  Start DHCP service on DC2 (netsh used to transfer properties).
                  Boot up some computers and see if it hits.

                  Yey? Ney?

                  Comment


                  • #10
                    Re: Switch DHCP to different server - clients fail

                    Almost in my oppinion

                    You're client will trying to get an IP of his DHCP server, which is unavailable.

                    Reduce lease time on DC1 to incredibly short time (ex. 1 hour).
                    Wait until the lease time has expired (eg. If the current lease time is 8 days, then wait at least 8 days)

                    Wait for the end of the work day to disable the DCHP service
                    Start DHCP service on DC2

                    Wait for one hour (new lease time )
                    Boot up some computers and see if it hits.
                    Marcel
                    Technical Consultant
                    Netherlands
                    http://www.phetios.com
                    http://blog.nessus.nl

                    MCITP(EA, SA), MCSA/E 2003:Security, CCNA, SNAF, DCUCI, CCSA/E/E+ (R60), VCP4/5, NCDA, NCIE - SAN, NCIE - BR, EMCPE
                    "No matter how secure, there is always the human factor."

                    "Enjoy life today, tomorrow may never come."
                    "If you're going through hell, keep going. ~Winston Churchill"

                    Comment


                    • #11
                      Re: Switch DHCP to different server - clients fail

                      This is what I might have done from the beginning:

                      Use NETSH to import the DHCP data
                      Deactivate the old scope (rather than just stopping DHCP service)
                      Activate new scope
                      Network Engineers do IT under the desk

                      Comment


                      • #12
                        Re: Switch DHCP to different server - clients fail

                        ...

                        I am obviously doing something very wrong.
                        Right now I have the old DHCP server's scope deactivated, and the new one up and running... Still cannot contact DHCP server...
                        I ipconfig /release'd and ipconfig /renew'd and I get:
                        An error occured while renewing interface Local Area Connection 2 : unable to contact your DHCP server. Request has timed out.

                        All computers are on the x.x.165.0/24 network, and DC2 is x.x.165.250. That's on the "broadcast network", right? Anything within .165.0/24, right?

                        I'm confused on how the client is suppose to broadcast a DHCP request to a network it's not "in". If the client has an IP of 169.254.x.x or 0.0.0.0 how does it broadcast to x.x.165.0? I can't ping any machines on .165.0/24 from the troubled client, which leads me to believe I shouldn't beable to broadcast to it. -- The ping is a problem... hrm...
                        I re-activated DC1 DHCP, release, renew, works... what is different about DC2...

                        Is there something in the hardware (switches, etc...) I'm missing?
                        Last edited by mmX; 15th November 2006, 02:31. Reason: Additional Content

                        Comment


                        • #13
                          Re: Switch DHCP to different server - clients fail

                          What is your DHCP scope? i.e. what is the range of IP addresses that your server will be leasing out to clients? Make sure DC2 is not in the scope. Also, check to see if the service is running.
                          Regards,
                          Jeremy

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

                          Comment


                          • #14
                            Re: Switch DHCP to different server - clients fail

                            Can you ping the DC2 when you got an IP from the DC1?
                            Marcel
                            Technical Consultant
                            Netherlands
                            http://www.phetios.com
                            http://blog.nessus.nl

                            MCITP(EA, SA), MCSA/E 2003:Security, CCNA, SNAF, DCUCI, CCSA/E/E+ (R60), VCP4/5, NCDA, NCIE - SAN, NCIE - BR, EMCPE
                            "No matter how secure, there is always the human factor."

                            "Enjoy life today, tomorrow may never come."
                            "If you're going through hell, keep going. ~Winston Churchill"

                            Comment


                            • #15
                              Re: Switch DHCP to different server - clients fail

                              First, I want to say: Thank you guys for looking at this, I really appreciate it.

                              Originally posted by JeremyW View Post
                              What is your DHCP scope? i.e. what is the range of IP addresses that your server will be leasing out to clients? Make sure DC2 is not in the scope. Also, check to see if the service is running.
                              The DHCP scope is .165.17 - .165.199. DC2 is .165.250
                              The service was running, I've actually just left it running now. And, I deactivated the scope to avoid conflicts.

                              Originally posted by Dumber View Post
                              Can you ping the DC2 when you got an IP from the DC1?
                              I can ping DC2 when I get DHCP from DC1. And, I can ping DC2 from DC1 when I run DHCP off of DC2. However, this is because DC1 (and DC2) has a static IP (.165.8 ), and both are outside the DHCP scope

                              Comment

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