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4.3.1.2.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 setting this switch to multilayer mode, and assigning an IP interface address to
the different VLANs. (See “Connecting VLAN Groups” on chapter 4.)

4.3.1.3.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.

4.3.1.4.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 the specified VLANs, and
pass the message on to all other ports. VLAN requirements are propagated in this way
throughout the network. This allows GVRP-compliant devices to be automatically
configured for VLAN groups based solely on endstation requests.
4.3.2.Forwarding Tagged / Untagged Frames
Ports can be assigned to multiple tagged or untagged VLANs. Each port on the switch is
therefore capable of passing tagged or untagged frames. To forward a frame from a
VLAN-aware device to a VLAN-unaware device, the switch first decides where to
forward the frame, and then strips off the VLAN tag. However, to forward a frame from a
VLAN-unaware device to a VLAN-aware device, the switch first decides where to
forward the frame, and then inserts a VLAN tag reflecting this port’s default VID. The
default PVID is VLAN 1 for all ports, but this can be changed (see chapter 2 “VLAN Port
Configuration” or chapter 3 “VLAN Port Configuration”).