Discover mode not working

Question

Hi. 
 I'm running Sophos XG Home virtual machine in unraid and trying to use it in discover mode. I followed the configuration guide in Deploy the firewall in discover mode - Sophos Firewall and configured my VM to have 3 network ports: one LAN, one WAN and one unassigned, which I then assigned as Discover port.

Then I turned on port mirroring on my Aruba switch and I can see from switch statistics and also from Unraid network monitoring that the traffic is being mirrored to Sophos XG Discover interface. 
 But now comes the problem: I'm not seeing any traffic in Sophos system graphs for Port 3. What am I missing here? Do I need to make a firewall rule for this to work? Shouldn't be required if I'm reading the documentation correctly.

Ilkka Ruuskanen · Answer

Just in case someone with the same issue finds this topic, the reason for this problem is that Unraid doesn't have support for promiscuous mode in virtual network interfaces. Promiscuous mode is needed for discover port to work when running the XG inside virtual machine. There might be a way to enable promiscuous mode by editing Unraid's config files but I'm not willing to go there.