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V
LAN
IRTUAL
S
VLAN Classification
When the switch receives a frame, it classifies the frame in one of
two ways. If the frame is untagged, the switch assigns the frame to
an associated VLAN (based on the PVID of the receiving port
(page 2-43 and 3-36). But if the frame is tagged, the switch uses
the tagged VLAN ID to identify the port broadcast domain of the
frame.
Port Overlapping
Port overlapping can be used to allow access to commonly shared
network resources among different VLAN groups such as file
servers or printers. Note that if you implement VLANs which do
not overlap, but still need to communicate, you can connect them
by using a Layer-3 router or switch.
Port-based VLANs
Port-based (or static) VLANs are manually tied to specific ports.
The switch's forwarding decision is based on the destination MAC
address and its associated port. Therefore, to make valid forwarding
or flooding decisions, the switch must learn the relationship of the
MAC address to its related port—and thus to the VLAN—at
run-time. However, when GVRP is enabled, this process can be
fully automatic.
Automatic VLAN Registration (GVRP)
GVRP defines a system whereby the switch can automatically learn
the VLANs to which each endstation should be assigned. If an
endstation (or its network adapter) supports the IEEE 802.1Q
VLAN protocol, it can be configured to broadcast a message to
your network indicating the VLAN groups it wants to join. When
this switch receives these messages, it will automatically place the
receiving port in the specified VLANs, and then forward the
message to all other ports. When the message arrives at another
switch that supports GVRP, it will also place the receiving port in
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