DC migration from 2003 to 2012 R2 - DNS/DHCP?

Vertigo

Vertigo

Vertigo

Soldato
Joined
28 Dec 2003
Posts
16,522
Hi,

About to migrate my DCs from 2003 to 2012 R2 and wondering what the best procedure is or whether anyone has any words of wisdom.

I'm totally fine with the process of migrating the DC itself, I'm more concerned with the DNS/DHCP servers and what the best way of doing this is.

My general instinct is to do each separately - get the new DC up and running then transfer the FSMO roles whilst leaving the DNS & DHCP on the 2003 box, then migrate each of those separately. Is this the best way or will it even work? Will the 2012 R2 DC be happy using DNS on a 2003 box or will it want to use its own?

As an alternative I could install DNS during the process of promoting the 2012 R2. Will this automatically replicate everything to the new DNS and I can then simply remove the old one?
 
When you set up the 2012 R2 DC, make it a DNS server for the same forest at the same time, it should then (assuming you made your zones AD published) get all the zones (forward and reverse) from the 2003 DC/DNS server. You can then retire the 2003 DNS at your leisure without having to do anything other than change your DHCP scopes (and any statically assigned devices) to point to the new DNS server (or add the old IP to the new server once the old one is decommissioned).

As for DHCP, I'd likely split the scopes across the two, then decommission the first and expand the scopes again on the new 2012 DC.
 
Cool thanks, I'll do it that way then :)

EDIT: Not sure how I'll handle the DHCP server yet, may just backup the database and throw it across to the new server.
 
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http://forums.techarena.in/active-directory/1298956.htm

Read the post by Meinoff Weber. It has some usual info in there like moving the time service. Definitely make the new DC the primary one in terms of dns and time service and roles.

I would do a backup and restore of the dhcp and create a split scope. Definitely don't just move without first making sure that all the scopes are working. I had a problem at one site where the phone system scopes refuse to work on 2008 dhcp. So its definitely worth taking your time.

I also recommend not rushing to demote the old DC.

edit: Actually the reason i did a backup and restore of the dhcp is because I already had a split scope across two 2003 dc and ended up replacing one of those with the new 2008 dhcp. So if you only have one dhcp, then just adding the dhcp role and creating a split scope would be the way to go.
 
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Ta for the advice, all going well so far although I've yet to migrate the DHCP server, just getting the domain itself sorted and FSMO roles transferred etc etc.

One thing that's always confused me though - Group Policy.

As I currently have a mixed environment with the new 2012R2 DC and two 2003 DCs, how exactly does Group Policy work? Everything has synchronised but, if I edit a policy on the new server, the hierarchy of options looks different.

For example, at the top level, the old servers show:

Computer Configuration
Software Settings
Windows Settings
Administrative Templates
User Configuration
Software Settings
Windows Settings
Administrative Templates

The new one however, shows:

Computer Configuration
Policies
Preferences
User Configuration
Policies
Preferences

Now I assume the latter is the new system/organisation and indeed appears to have new options I didn't have before. Can I start making use of these new policies even though my domain functional level is still 2003? Do I need (or should I) update the 2003 DCs somehow so they show the same options?

I've done some searching and read about CSEs but not sure exactly whether these are what I need to download and apply and, if so, to the 2003 DCs or clients.

Group Policy has always confused me slightly in this regard so if anyone has any advice it'd be appreciated :)
 
With regard to DHCP lease time, is it still advisable to change it to something very short during the transition?
 
I believe you can keep the same domain/forest levels, but extend the schema to take into account the new GPO options.
 
When we upgraded from 2003 to 2008R2 we just took our backup of the DHCP DB and restored it - as people have said, if you have a lot of reservations it's the simplest way.
We did want to migrate VLAN by VLAN, and the restore process suggests this is possible, but we never managed to get it to work - we just disabled all the scopes, and reenabled them as we moved them.

DNS we just ran side by side, and changed DHCP scopes to the new DNS servers as we went.

One thing that hasn't been mentioned is changing from FRS to DFS replication once you've raised the functional level - there's an MS post on it here.
 
paradigm said:
I believe you can keep the same domain/forest levels, but extend the schema to take into account the new GPO options.
Click to expand...

Yeah just been experimenting and it seems to work fine. I can set new options not available on the 2003 DCs and they are applied correctly at the client, even if the client obtains them from one of the 2003 DCs.
 
Just migrate your existing dhcp config and leases to 2012. It will take no more than 20 mins. No need to mess around with lease times or anything else.

http://blogs.technet.com/b/canitpro...ndows-server-2003-to-windows-server-2012.aspx

The only other thing I can think of that you may need to do is update switch configs to point to the new dhcp server if you have different scopes for ranges on multiple vlans (ip helper-address, or non-Cisco equivalent).
 
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