What is the simplest way to switch domain controller IP addresses from the Windows 2003 server to Windows 2012 server after migration?

Before promotion of the new Windows server 2012, they will be configured with static IP addresses. After promoting the 2 new Windows 2012 server DCs to our existing domain of 2 old Windows 2003 servers, I would like to have the new DCs take over the existing DCs IP addresses. Is this a simple demoting of the old DCs and then flipping IP addresses or should this be done before demoting the old 2003 DCs? Do I need to edit the "006 DNS Servers" for the new 2012 DCs in the DHCP scope options during the process or will a simple change of static IP address in the NIC settings of the 2 new 2012 servers be sufficient?
pgcITAsked:
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Cliff GaliherCommented:
I would strongly recommend against this. While, in theory, you can pull this off with a lot of planning, in practice it rarely works out well. Because of the way client caching works and a few other factors, at best it is an interruption of service, and at works it can break trust relationships with workstations. Once you pick an IP address for a DC, it is best to keep it.
Will SzymkowskiSenior Solution ArchitectCommented:
I would also recommend using different IP's for the new DC's. However if you are completely set on doing this the most reliable method would be the following...

- Make sure that DC1 (2003) and DC2 (2003) are primary and secondary DNS on all clients
- Demote DC1(2003) first
- Add the IP address from DC1(2003) to DC3 (2012) as a secondary IP (you do this from the network adapter properties on the IPv4 configure IP Settings)
- Now DC3 has 2 IP address (not 2 NIC's but 2 IP addresses on the same adapter)
- During this period your clients will communicate with DC2 (2003) which is the secondary IP on the DNS settings in the network adapter configuration
- Then you do the same process over again only doing it for DC2 (2003) and DC4 (2012)

Once you have done this and DC3 and DC4 have 2 IP addresses (their original one and the ones from the 2003 DC's) you can remove the original IP address that you gave them.

I have done this in a production environment with over 30,000 nodes so there was really no option to change all of the IP's over. I did do extensive testing to ensure that everything went smoothly, and using the above steps they did.

So like I originally said, if you can get around this by using different IP's this is the safest approach but if you are in an environment where there are thousands of nodes then you might want to follow the steps I have illustrated.

Will.

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vivigattCommented:
I would:

1.

Use new IP addresses for the new DCs

2.

Make sure that the new DCs can act as DCs. Especially, change the 006 DNS server to that of one of the new DCs and/or make sure that the domain members are using an IP address of a new DC as their primary DNS server.

3.

Remove the old DCs

4.

Then you can even add the IP addresses of the old DCs to the set of IP addresses assigned to the new DCs. But this sometimes have side-effects, especially if the addresses are not in the same subnet.
pgcITAuthor Commented:
Thanks for the responses.
Adding a second IP to the new servers, once the old DCs are demoted (one at a time), sounds very doable.
This confirms already what I thought would be the main issue going forward.
I have already setup a test environment. In the test environment I did change DC server IPs. My only problem was that test workstations needed a reboot. After that there were no issues.
Keep in mind a restart of all workstations is not a total disaster as this would affect only ~300 nodes.
Will SzymkowskiSenior Solution ArchitectCommented:
This change should be done out side of business hours. So tell your users to simply power down their PC and in the morning you will not have any issues. However i never had any issues like this in my environment. Test environment does not always test exactly like production but this issue you are running into keep it in your back pocket in case this is the same as production.

Aside from that you should be fine.

Will.
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Windows Server 2003

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