Can I update from Lion Server to Mountain Lion Server through Remote Desktop? I currently have a Lion Server providing DHCP for my network, and access that server exclusively through screen sharing over Apple Remote Desktop. I would like to upgrade from Lion Server to Mountain Lion Server, but am concerned that at some point during the process — especially since the server provides the DHCP service for my network, including the machine from which I access the server — I will be unable to access the server using ARD.

Can I perform the upgrade process entirely over ARD, or do I need to dig up a keyboard and monitor and connect them to the server box?
Basically, I think the answer is Yes if your server has an static IP, and your client is on the same network.

But that's in theory of course. For example, if both your computers are in a network without DHCP, they will assign themselves with an IP starting with 169.254., link-local IPs. Now, the computers know that each other exists, and can still connect to each other with that IP.

Now, the question is simple, you need to know what your server's IP is when the DHCP is gone, and no one can assign IP address to them. And since you won't know, put a static IP on, and it would work.

That's in theory again. But I've had situation like these, and it did work for me.

Anyway, good luck!