Allied Telesis AT-S60 - Manual (Page 239)

AT-S60 Management Software User’s Guide
Section II: Advanced Features 239
Another approach is to connect your VLANs with tagged ports instead of
untagged ports. A tagged port can handle traffic from more than one
VLAN at a time. For information on tagged and untagged ports, refer to
Chapter 18, Tagged and Port-based Virtual LANs on page 401.
You can also place different VLANs in different spanning trees. This is
accomplished using the Multiple Spanning Tree Protocol, explained in
MSTP Overview on page 258.