Allied Telesis AT-S63 - Manual (Page 284)

Chapter 25: Multiple VLAN Modes
284 Section VI: Virtual LANs
Non-802.1Q Compliant Multiple VLAN Mode
Unlike the 802.1Q-compliant VLAN mode, which isolates port traffic by
placing each port in a separate VLAN, this mode forms one VLAN with a
VID of 1 that encompasses all ports. To establish traffic isolation, it uses
port mapping. The result, however, is the same. Ports are permitted to
forward traffic only to the designated uplink port and to no other port, even
when they receive a broadcast packet.
Another difference with this mode is that the uplink port is untagged.
Consequently, you would use this mode when the device connected to the
uplink port is not IEEE 802.1Q compatible, meaning that the device cannot
handle tagged packets.
Note
When the uplink port receives a packet with a destination MAC
address that is not in the MAC address table, the port broadcasts
the packet to all switch ports. This can result in ports receiving
packets that are not intended for them.
Also note that a switch operating in this mode can be remotely
managed through any port on the switch, not just the uplink port.