Allied Telesis AT-S62 - Manual (Page 396)

Chapter 20: Tagged and Port-based Virtual LANs
Section V: Virtual LANs 396
❑ Tagged and Untagged Ports
❑ Port VLAN Identifier
Note
For an explanation of VLAN name and VLAN identifier, refer back to
VLAN Name and VLAN Identifier on page 388.
Tagged and Untagged Ports
You need to specify which ports will be members of the VLAN. In the
case of a tagged VLAN, this will usually be a combination of both
untagged ports and tagged ports. You specify which ports are tagged
and which untagged when you create the VLAN.
An untagged port, whether a member of a port-based VLAN or a tagged
VLAN, can be in only one VLAN at a time. However, a tagged port can be
a member of more than one VLAN. A port can also be an untagged
member of one VLAN and a tagged member of different VLANs
simultaneously.
Port VLAN Identifier
As explained earlier in the discussion on port-based VLANs, the
management software automatically assigns a PVID to each port when a
port is made a member of a VLAN. The PVID is always identical to the
VLAN’s VID, and that in a port-based VLAN packets are forwarded based
on the PVID.
Because a tagged port determines VLAN membership by examining the
tagged header within the frames that it receives, you might conclude
that there is no need for a PVID. However, the PVID is used if a tagged
port receives an untagged frame—a frame without any tagged
information. The port forwards the frame based on the port’s PVID. This
is only in cases where an untagged frame arrives on a tagged port.
Otherwise, the PVID of a port is ignored on a tagged port.