Create an interface with vlan 621 and 822 on your corporate router. Then assign it to a port or a switch out. Then connect yr modem to the corporate router first, then connect a cable from the corporate router to ma131.

It helps if u state what corporate router u r using. Easier for me to be more specific. Your ma131 wont be able to pass a vlan through, your corporate router most likely will.

This post has been edited by wanttotree: Jul 18 2019, 11:20 PM

Lol okay thats easy,
Example;
Create a bridge, name it br0 for example, bridge eth0 and eth1, then add vlan 621 and 822 under br0 interface.
From there u can plug fibre btu to eth0, and eth1 to yr ma131. I hope thats clear.

Woops my bad. I missed the usg part. U kinda need to do it by changing the json config file. Sorry i cant help with that. I did mine using a smart/managed swith in between. Cheers.