D-Link UWS User Manual
8. Use similar procedures to enable on port 0/2.
9. Force port 0/2 to be the root port for MST 20, which is the non-root bridge.
a. Go to the LAN > L2 Features > Spanning Tree > MST Port Configuration/Status page.
b. From the MST ID menu, select 20.
c. From the Slot/Port menu, select 0/2.
d. In the Port Priority field, enter 64.
e. Click Submit.
D-Link
Oct. 2015
Configuring Multiple Spanning Tree Protocol
Unified Wired and Wireless Access System
Page 684