It seems that the standard arp -s command (ARP -s inet_addr eth_addr) to statically bind a MAC address to an IP-address, no longer works on Windows Server even with elevated priviliges (administrator mode).
What does work? netsh interface ip add neighbors <Interface Name> <IP-address> <MAC-address>
Example: netsh interface ip add neighbors Ethernet 192.168.92.76 b4-0c-25-e3-c0-13