How to make sure server is primary DHCP server

I have a windows 2008 Standard 32 bit server.

I have a new Windows Server 2012 R2.

The 2008 was the original DHCP server.  I want the 2012 R2 to be the DHCP server.

DHCP is installed on both.

I tried the migration process I found on line and I hit a roadblock that stopped the migration process.

We have a single scope so I recreated it on the new 2012 R2.

When a computer boots that needs an address when you run ipconfig /all it shows it got the ip address from the 2008 server.

Can't I just remove the DHCP role from the 2008 computer?

Won't the 2012 R2 take up that role since it is already installed and configured?

Thank you
Jerry ThompsonAsked:
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David AtkinTechnical DirectorCommented:
Stop the DHCP server service on the 2008 server. Make sure it's started on the 2012.

Test DHCP on the clients. If they are getting it from the new server (after a reboot or ipconfig /release /renew) then you're good to remove the role of the 2008
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Hypercat (Deb)Commented:
The short answer is yes, and yes. However, if you're not careful you can end up with IP addressing conflicts when you haven't been able to export the old DHCP database and then import it into the new server database.  So, since it appears that you've created a completely new blank DHCP database on your new 2012 server, you need to be sure to avoid having your various devices trying to renew their DHCP addresses randomly, because that's almost sure to create conflicts with machines that haven't renewed their addresses yet.

What I would recommend is that you schedule a day/time when you can have all of your users shut down their machines overnight and then bring them back up in the morning.  At the end of that day, go in and stop the DHCP Server service on the 2008 server (you want to uninstall DHCP, but you don't necessarily have to do that immediately) and make sure it's running on the 2012 server.  That way, they'll all get new IP address leases from the new server the next morning and conflicts will be avoided.
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Lee W, MVPTechnology and Business Process AdvisorCommented:
As Hypercat points out, you need to be careful.

The point of DHCP is to assign IP addresses to clients.

If you want to move DHCP from one server to another, you need to pick one:
1. Migrate the existing database from one server to another (You said you hit a road block - what road block?).  This process shouldn't interrupt users and should be possible to complete in 15-30 minutes.
2. Use a split scope to migrate - narrow your existing scope - you can start by changing the lease duration to something VERY short - like 10 minutes - then you have to WAIT until all your existing clients renew their lease (should be HALF the time of the ORIGINAL lease term) AND reduce the range of IPs offered - if your scope was original 50-200, then change it to 50-125.  On the new server, set the scope to 126-200 - this way there won't be IP conflicts (make sure to note any exclusions/reservations).  This process could take days depending on what your initial scope is.
3. Stop the existing DHCP server, turn off ALL devices that get addresses via DHCP - this includes WIRELESS devices, Printers, computers, and anything else that might get an address.  Start the DHCP server on the new server (make sure it's authorized and a scope has been defined), and then turn everything on.  This process could take hours depending on how your network size and hot it is configured AND you can easily miss a device or two and end up with IP conflicts for the duration of their leases.
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Hypercat (Deb)Commented:
Also, there are a two common ways to handle static IP addresses - either through DHCP reservations or by creating exclusions within your scope to provide for devices that require static IPs. An additional point about starting out with a new, blank database, is to make sure that you recreate any DHCP reservations or exclusions that may have been created in your old DHCP database.
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Jerry ThompsonAuthor Commented:
I uninstalled DHCP from the 2008 machine and the 2012 Took right over.

Some of the considerations about users were not a problem at this time.  This is a school environment and since the students are gone and most teachers, the number of machines on is minimal.  So overall impact in case a mistake was minimal.

Thank you for all the feed back.  I just wanted to make sure there wasn't something additional to consider.

Regards,
jerlo727
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Jerry ThompsonAuthor Commented:
Thank you all.
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