Last update for the day:
Digging into the logs, I found this when I assign a VLAN tag to the VM:
Dec 28 15:24:53 TracheNodeA pvedaemon[1116]: <root@pam> update VM 42069: -net0 virtio=7E:EA:78:9D:EF:1F,bridge=vmbr0,tag=3
Dec 28 15:24:53 TracheNodeA kernel: vmbr0: port 2(tap42069i0) entered...