We setup Windows NLB (unicast) on 2 Windows 2016 servers. The HA and load balancing works as expected. However, I get these the host unreachable warning in the NLB manager from both servers. Sometimes, the warning disappears but most of the time are there.
I saw that MS suggests to use 2 NICs on NLB host for unicast mode. But I also saw reference about not needing it because UnicastInterHostCommSupport is used for above that is higher than 2003sp1 and I did see those registry keys in the OS.