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Albert WidjajaFlag for Australia

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Migrating DHCP & DNS first or DCPROMO first from 2008R2 to 2012 R2 ?

People,

I've got two 2008 R2 AD Domain Controller that is running also as Global Catalog in one of my AD site.
It doesn't run any of the FSMO roles, but it is currently serving as AD integrated DNS server and also DHCP server for the subnet.

I have deployed 2x Win 2012 R2 VMs but now I'm confused myself. Should I:

#1 Migrate both DNS and DHCP (I will setup DHCP resiliency in the two new 2012R2) first, then DCPROMO after
#2 DCPROMO the two new 2012 R2 VMs as DC/GC and then migrate both DHCP & DNS server

Which one is better or the most recommended way ?
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Patrick Bogers
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Thanks Todd,

So in this case, the two Powershell lines must be executed from the new Win 2012 R2 that has already installed DHCP role ?
or do I have to run it from each respective server ?

Patrick & Todd, this is just the deployment in one of the AD site, while in the main Data Center AD site, I already got one Physical machine running all FSMO roles.
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Hi Todd,

If I promote the two new servers as Domain Controllers + DNS AD Integrated during the business hours, would there be any outage or interruptions to the existing environment ?
There shouldn't be with those specific tasks.
OK, and lastly,

Do I need to reduce the DHCP lease to just 1 hour the day before the migration to make sure the cutover is quicker from the old server to the new server?
No.  The purpose of migrating dhcp is so you don't need to do that.
Ah I see,

So during the DHCP address lease, the IP is still working on the client, so by the time the lease is expired, the client would look for new IP and hopefully the Active-DHCP server will be answering the IP address request.

Is that correct ?
Correct.
Please reassign majority of the points to Todd for more thorough solution and responses to requester's follow up questions.