When you create a Trunk port on a Cisco device, that port is assigned every tag in the VLAN spectrum 1-4096 (if I'm not mistaken), allowing every configured VLAN on that device to send traffic across that Trunk .
XOS follows a more fine tuned approach: If you assign a single port multiple 802.1Q tags, it becomes a trunk port for only those two VLANs. And as your network grows, you can assign more VLAN tags to that port allowing it to ONLY send traffic from sanctioned VLANs. In terms of how to implement this, AlexandrP has outlined this in the comment above. I hope this helps
