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Migrating Static IP scheme to DHCP

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  • Migrating Static IP scheme to DHCP

    Hi all,

    Need some clarification.

    I have a small network of about 10 servers, NT and windows 2003. I have migrated the accounts and computers from the NT 4 domain to the Windows 2003 domain without issue. My problem now is that prior to me coming on aboard this small company, they employed a Static IP scheme, let say 192.12.X.X . That was fine but now the company is growing and i'm quickly runnning out of IP's to hand out. This is where DHCP comes in. But i have only 2 servers that are in the AD domain they are as follows:

    Server 1: is runnig DNS, is a DC,GC, File Server, holds all the FSMO roles.
    Server 2 is running Exchange 2003, DNS, DC,GC.

    These servers are loaded and maxed out on Memory 6-8 gigs each and maxed out on HDD space 500-600 Gigs each.

    My thoughts are to get a fresh windows 2003 server run DCPromo and create a new site in AD adn give it a 10.33.X.X range and create a site link to the default site. Create a New DHCP Scope then have the current 2 server then change there IP's to the new IP range and reboot. Then having the users pc use DHCP and have then reboot over a weekend to get the new IP's .

    have i missed something, overlooked a crucial element? forgotten something?

    Any comments would be greatly apreciated.

  • #2
    Re: Migrating Static IP scheme to DHCP

    First off, DHCP is not a resource-intensive service. Most people run it on a DC, especially in smaller networks. You don't say how many workstations you have, but if it's less then a thousand you can run DHCP on a DC. You don't have to, of course. If you have the money, by all means spend it on a dedicated server.

    If you are serious about redundancy though, consider a second DHCP server. Think about the scopes you will need.

    > create a new site in AD adn give it a 10.33.X.X range and create a site link to the default site.

    Why? I'm not following this at all. You only need a site if you have a WAN connection. You can add all sorts of subnets to one site, if you are thinking about the new IP scheme.


    • #3
      Re: Migrating Static IP scheme to DHCP

      Thank you for the reply,

      I have 220 total pc, servers, switches, and printers and with a class c network, i will run out, since we acquired another company and merging operations in the near future.

      So you think I should just a new subnet and then use that for the DHCP addressing for the clients...



      • #4
        Re: Migrating Static IP scheme to DHCP

        > So you think I should just a new subnet and then use that for the DHCP addressing for the clients

        What I'd do? OK. I would keep the same IP addresses, but use a different subnet. How about That will give over a thousand IP addresses without the need to change existing IP numbers. That way you will break less. Additionally, no need to route between an old and a new subnet. You will still need to change the subnet everywhere, of course.

        If you do decide to go for a new and additional subnet range, you just add that subnet to the current site (assuming same LAN).


        • #5
          Re: Migrating Static IP scheme to DHCP


          Thanks for the reply and for the info,

          All, thank you for the reply the info was good of course and i will make my decision soon.


          • #6
            Re: Migrating Static IP scheme to DHCP

            Generally IP conversion arenít that simple. There may be underlying dependencies that you may not be aware of at this time. I would suggest a slightly different approach. This approach should satisfy you goal of increasing the IP address rang as well as provide a level of safety with existing IP dependant resources. And will allow for growth into and beyond the upcoming merge. I will start with your existing network.
            You have a 192.x.x.x
            ( if you are using a valid public ip such as 192.12.x.x internally I would plan a move away into a private range such as 192.168.x.x.)

            Lets start by leaving the existing network intact.

            If you have a router at your core either a layer 3 switch or a router you will need an interface per subnet or a trunk so that the traffic is routable inside your gateway. Which I will assume is a firewall of some sort. If a router does not exist we can do all of the internal routing with your windows server.

            Using your forest root which I will call DC1 for the sake of this conversation Lets install a second NIC and DHCP.

            Configure DHCP for a range of address that will be well outside of the addresse in the upcoming merge. I would use something like 10.252.100.x/24 This should keep you well away from address in use in most enterprises.

            Address NIC #2 in that range.
            Configure DHCP to provide addresses in the effective range.
            Configure DHCP Scope options.
            Configure DHCP to update pointer addresses.

            On your switches create a separate VLAN for the new network range.
            On your Router configure static routing.
            Now on a host by host basis you can configure the machines to use DHCP, extend the VLAN to the machine all without breaking your network.

            Key devices will continue to function your users will never know the difference.

            This is an overview based on your submission I am sure that you can fill in the blanks. If more help is required submit back to the group.
            Regards and happy computing.


            • #7
              Re: Migrating Static IP scheme to DHCP


              Thank you for the reply, you brought a very good case and it looks good I will add this to my collection here and decide the approach that I will take.

              Again thank you very much, I appreciate it.