Domain Controller, DHCP, and DNS migration

I am planning on migrating a physical Windows 2008 r2 server to Windows 2012 r2.  This server has the following Roles:
AD DC, DNS, and DHCP. My question is: Are there any repercussions for changing the IP address of a server hosting DC, DNS, and DHCP?

Or can I use the IP address of the retired server?  What is the best practice or approach in this matter?

sergio vegasystems administratorAsked:
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Cliff GaliherCommented:
You can go wither way with planning. My recommendation is to not change the IP address of a DC once promoted. Your old and new DC can coexist for a time while you teat and verify that you've properly changed over DNS settings on client devices, etc. Thus that is usually tone safer and easier route.

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Chris HInfrastructure ManagerCommented:
If you can afford downtime, you can do a 2008r2 to 2012r2 in-place upgrade with your installation media.  The process usually takes about 2-2.5 hours, including post operations testing.

This would maintain ip address and DNS functionality, causing the least amount of disturbance (minus downtime) in your environment.  It's usually the way I like to go.
Chris HInfrastructure ManagerCommented:
I'd definitely recommend making a clone of your domain controller (off the network!) and testing the in-place upgrade.
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It is best if you can reuse the same IP after it is up and running. If you cannot, just make sure you have changed your DHCP options to assign the right DNS servers to clients and also make sure you change your IPhelper config to point to your new DHCP server on your switches if using vlans.
sergio vegasystems administratorAuthor Commented:
Thanks for all your comments.

The plan is to replace the old physical server and move these roles to a new physical or VM Server.

What I was trying to avoid is having to change any network devices that are statically pointing to the old DNS server.

I was looking for your advice and recommendation in this matter.


Will SzymkowskiSenior Solution ArchitectCommented:
If you can afford downtime, you can do a 2008r2 to 2012r2 in-place upgrade with your installation media
Althought this is possible i would not recommend doing an in-place upgrade. As you can always run into issues while doing these and also it does require down time. Whenever i have done this type of migration i always spin up the new server and the migrate the services over.

Are there any repercussions for changing the IP address of a server hosting DC, DNS, and DHCP?

You can use the same IP but what I would recommend is the following...
- bring up the new server 2012R2 (promote as a DC/GC with NEW IP)
- point your DHCP clients to the new IP as a secondary DNS IP (also static addresses as well on servers)
- Ensure replicaiton is working properly
- Demote your 2008R2 DC
- Change the IP Address of the 2008R2 server to a new IP
- Update your VLANs with the DHCP helper address of the new IP you gave to 2008R2

***The above step is only required if you have multiple VLANs and your DHCP server is on a different VLAN than your workstations, or any other devices trying to get a DHCP address***

- Make sure you keep the old 2008R2 IP in the dhcp helper address because it will be used once you trasnfer the DHCP role to 2012R2 DC
- Add the old 2008R2 IP as an additional IP to the 2012R2 DC (now you have 2 IP on the same NIC)
- Ensure replicaiton is working after demotion
- Uninstall DNS from the 2008R2 server that was demoted (this does not happen automatically)
- Change the dhcp scope for DNS to point to the Original 2008R2 DC IP (which is now on 2012R2 DC)
- Remove the Original 2012R2 IP from DHCP scope for DNS
- Migrate the DHCP to the 2012R2 DC
- Remove the 2008R2 machine from the domain (if not longer being used)
- Rmeove the original IP for the 2012R2 DC server, leaving only the Origainl IP address, which is now transferred

Also i would highly recommend making sure that you have atleast 1 other domain controller in the mix to ensure that you have high availability for your DC/GC/DNS.

Aside from that, you should be fine.

Will SzymkowskiSenior Solution ArchitectCommented:
WOW all that and answer was accepted before i posted!

sergio vegasystems administratorAuthor Commented:
Hi Will,

I guess, I got ahead of myself. Your recommendation is exactly the answer I was looking for.  The next time, I won't be so darn quick to give points out. ; )

I am just thinking ahead of a DC migration project coming up my way soon.  I will look for you next time I post something related to this subject.

Best Regards,

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