Going to turn off DHCP on 2003 server and authorise on 2012 server before expiring

I have a 2003 DC I'm replacing with a 2012.  I have DNS pointing to the new 2012 machine already and am ready to turn off the 2003 and bring up 2012, but have DHCP down to 2 hours but wanted to know should I turn it down before expiration or after?  They all expire around 9-10am.
bergquistcompanyAsked:
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BurundiLappConnect With a Mentor Commented:
I would turn it off before expiration but after most of your workstations have been started and have received an IP.

If you have use half the range or less then you don't need to worry about duplicates, you could put an exclusion range on the 2012 server for the ones that have been assigned by the 2003 server, once the 2003 DHCP leases have expired you could then remove the exclusion and let the addresses be given out by the 2012 server, that should prevent duplicates being given out.
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Thomas GrassiSystems AdministratorCommented:
IF you shutdown DHCP now then the computers will still have an ip address it will try to obtain a new lease and it will not since the DHCP server is down.

How many computers we talking here?

You more than likely will have to do a few ipconfig /release and ipconfig /renew

maybe even ipconfig /flushdns on some.

Best to switch over off peak hours with minimal access.
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wicadaConnect With a Mentor Commented:
I would unauthorize the old and authorize the new DHCP server. If we were talking about a small amount of users, I would have them all reboot or I would wait until the lease expires and they all renew their lease with the new DHCP server before I shut down the old dhcp server.
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bergquistcompanyAuthor Commented:
100 machines

so if we unauthorize and authorize the new can the new give out an IP that somebody already has leased from the old?
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wicadaCommented:
Yes, you can export the dhcp information from the old server to the new one also.

On the old server:

netsh dhcp server export \\server\share\dhcpConfig.dat all (Export DHCP information to the specified path\file)

On the new server:
netsh dhcp server import \\server\share\dhcpConfig.dat all (Imports DHCP information from the specified path\file)

After, you will want to stop the DHCP and Start the DHCP service on the new server. If you do this you should be able to unauthorize the old DHCP server at any time and authorize the new one. All the lease information will be in the new server.


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Sarang TinguriaSr EngineerCommented:
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