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  • DHCP Migration Question

    Hello. I have read over some of the posts regarding this, but am a little confused between two things.

    Got an 03 domain. One 08R2 server. Am working on converting the other 03 servers to 08 one at a time. One of these 03 servers is hosting DHCP which has about 40 scopes, 7297 addresses with 1068 in use. Like the other posts, I need minimal downtime with whatever gets done keeping the same address as the old server had.

    I have read two processes, one using the netsh command where you export/import the dhcp db etc. and the other where you use the new 08R2 Migration tool. What is the difference though?? Apparantly both are solutions but the 08 tool takes longer. The server that hosts DHCP is also the primary DNS server. So this would actually be a two step process. Moving DHCP and DNS to another server running 08R2 that will have the same ip address as the original.

    Can someone offer some guidance on this, suggestions, differences. Please.

    Thanks
    Chris

  • #2
    Re: DHCP Migration Question

    The Netsh option seems to be the safest bet. There has been an issue identified with the GUI option.
    http://support.microsoft.com/kb/962355
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    • #3
      Re: DHCP Migration Question

      No downtime is needed. Not at all in fact.

      How many reservations do you have? You can pretty simple script it with powershell and Netsh.
      When the new DHCP server is in place, simply disable the old one and enable the new one.

      Your clients will broadcast for a new IP lease when the former server is down. If you read the RFC about DHCP you know it's process and you'll know you don't need any downtime.

      The same basically for DNS. Add an additional DNS server and just re-create the static records. Let the clients recreate there own record or... When you've AD integrated DNS it will get the existing records. Just set the IP address in the DHCP scope (and on your servers) when the DNS server is ready to use.
      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"

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      • #4
        Re: DHCP Migration Question

        Thanks I will give the ms article a try as soon as I can get this scheduled. Since there are so many systems that point to this server's IP address, my plan is to do the backup from 03 as indicated, change the IP on that server to something else, change the IP on the new 08 server to what the other was and then continue the process. That way everything that is pointing to this DHCP server by IP will keep working. This will also be a DC.

        As for DHCP there are currently 40 scopes. 7297 total addresses with 1061 in use.

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        • #5
          Re: DHCP Migration Question

          What systems point to the IP from a DHCP server?
          If it's DNS ok, but for DHCP it should be only the IP Helper Addresses on your network components.

          Still if a client got a lease, he will try to renew it half way. If the DHCP server is unavailable he will continue retrying (every time half way) until it's current least until it's expires.

          So fo example: Lease time = 8 days: renewing: 4 days, 2 days, 1 day etc. There might be some civets depending on the client and the lease time. But you get the idea.

          However, for DNS, that might be a pain in the but to reconfigure you're servers, however you might set a secondary address on the new server for the time being until you reset all the other servers to the new DNS server. Or you might be able to script it using PowerShell, WMI or whatever you can use

          Again, read the RFC for DHCP for a in depth knowledge about DHCP:
          http://www.ietf.org/rfc/rfc2131.txt

          Also you didn't respond to my question, how many reservations. I really don't care about the current leases, but about the reservations.
          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"

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          • #6
            Re: DHCP Migration Question

            Thx Dumber. Looking through the scopes there are no reservations setup. We pretty much are still using static addressing domain wide with the exception of a few areas which are DHCP only, with no reservations.

            As for what systems point to the DHCP server by address, not to sure. I was told that but have not verified. They may have been referring to DNS that is also hosted on that box.

            I already have all the DNS zones AD integrated. As it stands now I'm going to install a new server, get 08 R2 on it then look at moving over to is from this one. I'll need to use the same IP address, but I have two secondaries up and running. So the only prob I can see is if clients dont fail over to their secondary dns address for the few minutes the change is occuring.

            I am guessing that I want to dcpromo this box before I install DNS and DHCP roles?

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            • #7
              Re: DHCP Migration Question

              You certainly want to DCPROMO first -- then add DNS (an option when you are promoting anyway in 200

              I suggest you shorten the life of your current DHCP scope to say 1 hour NOW, so the switchover will be quicker.

              Not done it with a network on your scale, but normally I deactivate the old scope and activate the new -- clients will attempt to keep their old IP address on a renewal, so no data migration has been necessary.
              Tom Jones
              MCT, MCSE (2000:Security & 2003), MCSA:Security & Messaging, MCDBA, MCDST, MCITP(EA, EMA, SA, EDA, ES, CS), MCTS, MCP, Sec+
              PhD, MSc, FIAP, MIITT
              IT Trainer / Consultant
              Ossian Ltd
              Scotland

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              • #8
                Re: DHCP Migration Question

                I've done it on a pretty large scale, an environment with 1200 DHCP scopes.
                2 dedicated servers just for DHCP.
                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

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