Proxmox works as vlan but doesn't work well as a Trunk for Cisco WLC 9800

[monkeybear202020]

giga 1 is for MGT / out of band modem <-- which is forced
Giga 2 is for Data and Trunk and I'm stuck here <-- this is what I need to use

 

[shanreich]

What exactly isn't working / What are you trying to achieve? I cannot really tell from your initial problem description.
How does your network configuration look like (/etc/network/interfaces).
How does the network configuration inside the VM look like?