Specifications

VLAN Configuration
2-83
2
This switch supports the following VLAN features:
• Up to 255 VLANs based on the IEEE 802.1Q standard
• Distributed VLAN learning across multiple switches using explicit or implicit tagging
and GVRP protocol
• Port overlapping, allowing a port to participate in multiple VLANs
• End stations can belong to multiple VLANs
• Passing traffic between VLAN-aware and VLAN-unaware devices
• Priority tagging
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 if you want it to carry traffic for one or
more VLANs, and any intermediate network devices or the host at the other end of
the connection supports VLANs. Then assign ports on the other VLAN-aware
network devices along the path that will carry this traffic to the same VLAN(s), either
manually or dynamically using GVRP. However, if you want a port on this switch to
participate in one or more VLANs, but none of the intermediate network devices nor
the host at the other end of the connection supports VLANs, then you should add
this port to the VLAN as an untagged port.
Note: VLAN-tagged frames can pass through VLAN-aware or VLAN-unaware network
interconnection devices, but the VLAN tags should be stripped off before passing
it on to any end-node host that does not support VLAN tagging.
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.
Untagged VLANs – Untagged (or static) VLANs are typically used to reduce
broadcast traffic and to increase security. 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