Allied Telesis AT-S29 - Manual (Page 123)

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Forwarding
Tagged/
Untagged Frames
Ports can be assigned to one untagged VLAN and multiple tagged
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, but this can
be changed (see page 2-35 or 3-25).
Forwarding
Traffic with
Unknown VLAN
Tags
Up to 2048 VLANs are supported by the IEEE 802.lQ protocol, but this
switch only supports 16 VLANS. Therefore, if this switch is attached to
any device that forwards frames with unknown VLAN tags, or to
endstations which issue VLAN registration requests for unknown VLANS,
this traffic will be dropped.
Automatic VLAN
Registration
GVRP defines a system whereby the switch can automatically learn the
VLANs each endstation should be assigned to. If an endstation (or its
network adapter) supports the IEEE 802. 1 Q 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.
VLAN aware VLAN aware
VLAN aware VLAN unaware
VLAN aware
VLAN aware
trunk
VLAN 1, 2, 3
(802.1Q tags)
VLAN 1, 2
(802.1Q tags) VLAN 1, 3
(802.1Q tags)
VLAN 1, 2, 3
(802.1Q tags) VLAN 1, 3
(untagged)