Assigning Ports to VLANs
Before enabling VLANs for the switch, you must first assign each port to the
VLAN group(s) in which it will participate. By default all ports are assigned to
VLAN 1 as untagged ports. Add a port as a tagged port (that is, a port attached
to a VLAN-aware device) if you want it to carry traffic for one or more VLANs and
if the device at the other end of the link also supports VLANs. Then assign the
port at the other end of the link to the same VLAN(s). However, if you want a port
on this switch to participate in one or more VLANs, but the device at the other
end of the link does not support VLANs, then you must add this port as an
untagged port (that is, a port attached to a VLAN-unaware device).
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. 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 deci-
sions, 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.
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