Allied Telesis AT-S24 - Manual (Page 106)

Configuring Virtual LANs and Quality of Service
106
If the connected device is a legacy device (i.e., a device that does not
support or act upon VLAN tagging), there are addition methods for
handling the frame.
As described in the port-based VLAN section, an untagged incoming
frame needs to have a VID inserted or associated with it so that the
frame can be properly forwarded throughout switch. Consequently,
each port is required to have a VLAN tag associated with it; this port-
based tag is referred to as the Port VLAN ID (PVID). The port’s PVID is
inserted into the frame and is used as the frame’s VID as the frame is
passed through the switching system.
The port PVID assignment enables legacy (non-802.1Q compliant)
devices connected to the switch to take advantage of the VLAN and QoS
capabilities of the switch.
Note
The management port of this switch is a legacy device. It cannot
interpret VLAN tags. The management agent responds only to
communications from devices that are located within the same
VLAN, defined by the management port’s PVID.
VLAN Tagging Example. Figure 52 illustrates how tagged ports can be
used to interconnect IEEE 802.1Q-based products. The example uses
tagged ports to provide an uplink between an AT-8224XL Switch and an
AT-8518 Switch. A tagged port is also used to connect an IEEE 802.1Q
compliant server to a switch so that the server can be shared among
multiple VLANs without the need for a router.