Windows server 2016 TP5: network cross icon despite no obvious problems

I have set up a lab server with W2016TP5, and it runs (more or less) fine. The static IP and subnet seem correct, and the DNS and DHCP servers and a bunch of Hyper-V linux VMs seem to be all fine. However, the taskbar shows permanently a "network broken" sign (see picture). Ruing the windows diagnostics does not identify anything wrong. Ipconfig yields the following:

Etheet adapter vEtheet (ExtealTo02):

Coection-specific DNS Suffix  . :
Link-local IPv6 Address . . . . . : fe80::f142:1a28:5a28:9821%24
IPv4 Address. . . . . . . . . . . : 10.10.10.2
Subnet Mask . . . . . . . . . . . : 255.255.0.0
Default Gateway . . . . . . . . . : 10.10.10.1

Tuel adapter Local Area Coection* 2:  

Coection-specific DNS Suffix  . :
IPv6 Address. . . . . . . . . . . : 2001:0:5ef5:79fd:20f3:1fc6:f5f5:f5fd
Link-local IPv6 Address . . . . . : fe80::20f3:1fc6:f5f5:f5fd%4
Default Gateway . . . . . . . . . : :: 

Tuel adapter isatap.{FBE44E52-FFC9-468B-83EC-F635E09E2F5E}:

Media State . . . . . . . . . . . : Media discoected
Coection-specific DNS Suffix  . : 

Are there any conditions of misconfiguration that are not detected by usual lan diagnostics, and yet cause the taskbar net icon to raise a flag?