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VLAN Configuration
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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
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.
To implement GVRP in a network, first add the host devices to the required VLANs
(using the operating system or other application software), so that these VLANs can
be propagated onto the network. For both the edge switches attached directly to
these hosts, and core switches in the network, enable GVRP on the links between
these devices. You should also determine security boundaries in the network and
disable GVRP on the boundary ports to prevent advertisements from being
propagated, or forbid those ports from joining restricted VLANs.
Note:
If you have host devices that do not support GVRP, you should configure static or
untagged VLANs for the switch ports connected to these devices (as described in
“Adding Static Members to VLANs (VLAN Index)” on page 3-162). But you can still
enable GVRP on these edge switches, as well as on the core switches in the
network.
Port-based VLAN
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