And the guest network is setup as vlan only with correct vlan id?
99% certain I've got the right network port chosen for the VLAN.OPNSense is running in an Hyper-V instance with a dedicated dual NIC (one NIC for WAN and one NIC for LAN).
And there I see the problem. Are you sure that Hyper-V is supporting to set the VLAN inside of a virtual machine? I always had issues with VLANs inside of a virtualized environment. I created them in the hypervisor to get them working. And if I remember correctly there was a thread where someone run into the maximum number of networks for OPNsense inside a Hyper-V VM because it only worked if the VLANs were created in Hyper-V.Try to create a VLAN in Hyper-V and assign it as a interface in the OPNsense VM.KH
Would this mean, then, that I need another physical NIC connected to it's own virtual switch and everything tagged with the VLAN?