VLAN C
ONFIGURATION
13-4
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 default VLAN ID 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
enabled routing on this switch.
Untagged VLANs – Untagged (or static) VLANs are typically used to
reduce broadcast traffic and to increase secu rity. A group of network users
assigned to a VLAN form a broadcast domain that is separate from other
VLANs configured on the switch. Packets are forwarded only between
ports that are designated for the same VLAN. Untagged VLANs can be
used to manually isolate user groups or subnets. However, you should use
IEEE 802.3 tagged VLANs with GVRP whenever possible to fully
automate VLAN registration.
Automatic VLAN Registration – GVRP (GARP VLAN Registration
Protocol) defines a system whereby the switch can automatically learn the
VLANs to which each end station should be assigned. If an end station (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