To do this on recent Fedora and Arch, it is necessary to set
dhcp-client-identifier = hardware to get DHCP to work. I suspect the same is true on 17.10. However, Artful uses netplan and systemd-networkd.
For the latter I can set
In /etc/systemd/network/(interface name).network, which overrides /run/systemd/network/10-netplan-(ifname).network.
I'd prefer to set this in the file /etc/netplan/01-netcfg.yaml, or something in /etc/netplan/.
These are specifics of how the above might be solved, though. The overall question is how to use the MS Windows Server 2012 DHCP server with MAC reservations with Ubuntu 17.10 server using netplan. I may be able to request reconfiguration of the DHCP server if it won't have a significant effect on other clients, or can be done per-reservation somehow.
(I'd have used the tag windows-server, but it doesn't exist for some reason)