Disconnecting WAN on one VM also disconnects it on others?

[JBB]

Using PVE 4.4-22/2728f613 with the following config for a Linux VM:

net0: virtio=C2:75:29:81:BE4,bridge=vmbr0,firewall=1
net1: virtio=36E:0C:03:12:1B,bridge=vmbr1

net0 is the WAN interface, which I need to disconnect. However, when I do (using the PVE GUI) the WAN on another VMs goes down as well.

It only seem to affects one other VM though. Other VMs remain connected. Is there something on the guest that I'm missing?

I've tried fire-walling it off, but can't work that out either (a single inbound DROP rule doesn't do it).

I'd be grateful for any clues...

 

[JBB]

After some more investigation, I still have no clue as to why this might be happening. So I'm just going to drop WAN traffic from inside the guest in question.