Forwarding Traffic With Unknown Vlan Tags; Forwarding Tagged/Untagged Frames; Connecting Vlan Groups - Alcatel OmniStack 8008 User Manual

Advanced Topics
This allows GVRP-compliant devices to be automatically configured for VLAN
groups based solely on endstation requests.

Forwarding Traffic with Unknown VLAN Tags

This switch only supports 256 VLANs with VLAN IDs ranging from 1 to 2048, but the
IEEE 802.1Q VLAN standard allows for VLAN IDs from 1 to 4094. Therefore, if this
switch is attached to endstations that issue VLAN registration requests, it will have to
forward unknown VLAN tags. This traffic can only be propagated to the rest of the
network if automatic VLAN registration is enabled on your switch.

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 page 2-47 or page 3-30).

Connecting VLAN Groups

The switch supports intra-VLAN communication using wire-speed switching.
However, if you have devices in separate VLANs that must communicate, and it is
not practical to include these devices in a common VLAN, then the VLANs can be
connected via a Layer 3 switch or router.
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