Advice Required - Migrating Domain Controllers from 2008 to 2008R2

Hi all,

Our existing domain consists of the following (3 x DC's):

OLDDC1 - Server 2008 (32bit) (This is the Primary DC)
OLDDC2 - Server 2008 (32bit)
DC3 - Server 2008R2

We are in the early stages of planning the migration of OLDDC1 & OLDDC2 to 2008R2.

I am looking for the best way to do this, when considering the following queries....

1.) We would like the new DC's OLDDC1 & OLDDC2 to be renamed DC1 and DC2 so that their naming convention falls in line with the rest of our servers.  I am concerned about what this might break though if software/hardware is configured to reference the DC's (via LDAP etc) by their server name.  What is best practice here?

2.) Ideally I would like to run the new DC's side by side with the old DC's for a while as we transfer roles.  Is this possible?  Again, I am concerned about software/hardware which reference the DC's via their IP address (e.g. NIC's with static DNS settings) .  

With this in mind is it going to be viable to run them side by side and then switch IP's etc? What is best practice here?

I am sure more questions will come to me but I think that is a good starting point!
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Peter HutchisonSenior Network Systems SpecialistCommented:
1. For ldap we try to set up a service name e.g., we also keep the old server names in DNS and point them to the new servers using CNAMEs so if you miss anything, the names will still resolve.

2. The only thing that would use IP address would be DNS entries in TCPIP settings. So you would need to identify which servers are using them and then update them to point to new servers.
Any applications will need to be changed and ip addresses should be changed to dns names where possible.

As for switching IPs you can only do that once the old server is demoted and switched off and then the IP applied to new server before it is promoted to a DC.
The time for a DC becomes promoted depends on number of objects in AD and files in Sysvol, so expect at least 1/2 a day for completed switchover per server.
Dan McFaddenSystems EngineerCommented:
What I recommend is the following:

1. verify where all your FSMOs (all 5) are located.  I'll guess this is what you mean by PDC.
2. move all the FSMOs to DC3.  This will have no ill effect on your infrastructure.
3. identify what software/hardware is configured to use the hostnames of the old DCs.
3a. if these things use the IP, that is fine
4. build the new servers, but do not DCPROMO them just yet
5. take one of the old DCs offline by doing a DCPROMO to demote the server
5a. how to link:
5b. write down the old DC's IP, this will be used later
6. after demoting the old DC, disable the NICs and disconnect from the network
7. run a full verbose DCDIAG check to verify no errors exist in AD after the removal of the old DC
7a. reference link:
8. on 1 of the new DCs, reconfigure it to use the IP of the old DC that was just demoted
9. reboot new server
10. do DCPROMO to put this server into the domain as a DC
11. repeat steps 5 thru 10 for the other old DC and new server

Essentially you are reusing the existing IPs of the old DCs, this way preserving any direct IP references to the old DC IPs.  If necessary, you could then create CNAMEs in DNS pointing OLDDC1/2 to the new DC names.  This can preserve any hard coded hostnames pointed at OLDDC1/2.  Though I recommend trying to eliminate any hard coded references.


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fieldjAuthor Commented:

That sounds like great advice.

I am going to take a little time to digest all of that information, but it looks like a perfect solution.

I will have a think about it all and get back to you if I have any further questions.

Thanks again
fieldjAuthor Commented:
Excellent plan of action, thanks for the advise.
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