We recently migrated our Windows Server 2003 based DHCP Server to Windows Server 2008 R2 because I wanted to use Network Access Protection to improve our network security. After half an hour the software was installed and I started to configure the DHCP server. I quickly defined scope, NAP configuration, and all the other options and all I had left to do was move the DHCP reservations to the new server. I had no intention of transferring the addresses manually—it’s not that I am lazy, but copying and pasting many items is an error-prone process—and so I started looking for a migration tool.

Microsoft’s GUI for managing DHCP doesn’t provide any solution for this matter. Gladly I found a script called the DHCP Reservation Manager that does exactly what I needed: automatically migrate DHCP reservations. You can read about its features here. The tool offers four options:

  • Migrate reservations from one DHCP server to another
  • Synchronize reservations between two DHCP servers
  • Dump leases
  • Read reservations from a text file

In my case I just had to type the following command:

cscript rmanager.vbs Rmanager –migrate 192.168.1.1 192.168.1.2 all

The script correctly transferred all reservations to the new server. However, I realized that the script didn’t copy the description field of the reservations. As our organization no longer uses this field this was not a problem.

If you don’t want to synchronize every scope to another server, you can still use the tool because it allows you to identify which scopes to transfer. You can limit the scopes by adding them to the command:

cscript rmanager.vbs Rmanager –migrate 192.168.1.1 192.168.1.2 192.168.1.0 192.168.2.0 192.168.3.0

This command would add the reservations from the three subnets 192.168.1.0, 192.168.2.0, and 192.168.3.0 to the DHCP server. I don’t want to go into more detail here because the blog entry at blogs.technet.com is quite comprehensive.

This tool saved me a significant amount of time and made the migration as smooth as it can be. Everybody’s reserved IP address was retained after the old server was switched off. I doubt that this would have been the case if I would have moved them manually. Until Microsoft includes such a feature in the GUI, this tool is an acceptable alternative for managing DHCP reservations.

DHCP Reservation Manager ^

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4 Comments
  1. BT 10 years ago

    Just curious - with the flexibility in private IP addressing why not just expand your subnet range so that you can isolate DHCP from static devices? Seems a hassle to maintain reservations.

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  2. Author
    Alexander Weiß 10 years ago

    I agree that they are a hassle to maintain, but it also has some advantages:
    - centralized management
    - no manual interaction with the client needed
    - if you use WINS no restart is needed when the WINS DB is lost
    I clearly prefer the solution you described. 95% of our clients are in private subnets. There are some necessary excpetions, though.

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  3. BT 10 years ago

    Gotcha - thanks for sharing your solution.

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  4. Shawn Allin 9 years ago

    Hi,
    was it difficult to figure out how to add all the fixes to the rmanager script that were discussed?
    Preferably, could you provide the finished product? 🙂

    Thanks,
    Shawn

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