Hello Eugene, Glad to hear that you were able to find a solution to your problem. Looking over the information that you have provided, it does sound like the solution that you have come upon is correct. By setting the Trunk ports up with 1UP only, the traffic on VLANs 30 and 40 were never actually leaving the devices. By allowing 30T and 40T, the ports were configured to pass along the additional VLANs on the ports with additional header information that allows the devices to tell the VLANs apart once received. Please let us know if the solution you found does resolve your issue on the production network, and if so, please remember to mark your post as resolved and rate any helpful responses. If you wind up running in to any other issues, please report back and we'll see how we can help! Also, for anyone coming to this issue in the future, the Knowledge Base has a few resources to help with configuration of devices: Configuration of VLAN Membership of an Interface on the 200/300 Series Managed Switches Enabling Multiple Wireless Networks on RV320 VPN Router, WAP321 Wireless-N Access Point, and Sx300 Series Switches Thanks again for using the Small Business Support Community!   ... View more