Why do I get this "gateway range likely lacks support" message?

netcheck: probePortMapServices: skipping portmap; gateway range likely lacks support

That isn’t really an error: tailscale can send UPnP and NAT-PMP probes to try to open firewall ports. It tries to only do this if it thinks it might be in a residential environment:

  • has a private IP address like 192.168.1.x
  • its default route is another private IP address on the same net

In particular, when running in various cloud environments, tailscaled skips sending UPnP and NAT-PMP probes because it isn’t useful.