Migrating DHCP when using DHCP failover

[robk]

We have 4 DCs, 3 out of 4 have now been upgraded to Server 2022 (from Server 2012 R2).

 

The last DC holds several FSMO roles (but that will move when I demote it)

 

The snag is that the last DC is also the DHCP server for all our subnets, with failover configured to 2 different DCs for different buildings.

 

Whats the best way of migrating this?

 

I could delete all the fail over configs, basically rebuilding DHCP from scratch, but that's going to create down time.

 

Export-dhcpconfig does not appear to include failover info.

 

Is there a way I can backup the DHCP server, remove from the "old" DC1 and restore to the "new" DC1?

[Steve21]

You could just disable the failover on the one you're demoting, and then re-enable it after the upgrade?

 

What makes you think it'll give you downtime? The 2nd partner of the failover should just keep running as a single DHCP, and you can re-add a new failover unless I'm misunderstanding what you mean

 

*Edit - or do you mean there's only 1 DC at the main site?

 

Steve

[robk]

The docs I read seemed to indicate deleting the failover removed the subnet from both servers. Hence the down time.

[Primus]

The docs I read seemed to indicate deleting the failover removed the subnet from both servers. Hence the down time.

 

It doesn't.

[Julian]

DHCP and FSMO are seperate, so you can promote a diffrent server to FSMO with affecting DHCP.

 

Try changing your DHCP mode to "Load balancing" for all your ranges, and then check the statistics to see that multiple servers are giving out DHCP addressees. That way you can safely take down any DHCP server, knowing that the network dhcp will still function.

 

If you are doing a inplace upgrade to Server 2022, then the existing settings will be retained. If it is a clean build, you will have to reconfigure the failover, when the new server is running.