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Port-based VLANs 277
Dynamic Port-based
VLANs Using GVRP
For Multilayer Switching Modules, GARP VLAN Registration Protocol
(GVRP) can help you simplify the management of VLAN configurations in
your larger networks.
GVRP allows the Multilayer Switching Module to:
■
Dynamically create a port-based VLAN (unspecified protocol) with a
specific VID and a specific port, based on updates from GVRP-enabled
devices
■
Learn, on a port-by-port basis, about GVRP updates to an existing
port-based VLAN with that VID and IEEE 802.1Q tagging
■
Send dynamic GVRP updates about its existing port-based VLANs.
GVRP allows your Multilayer Switching Module to advertise its manually
configured IEEE 802.1Q VLANs to other devices supporting GVRP.
Because the VLANs are advertised, GVRP-aware devices in the core of the
network do not need manual configuration to pass IEEE 802.1Q frames
to the proper destination. The method of VLAN advertisement used by all
GVRP-capable switches involves protocol data units (PDUs), similar to the
method used by STP. GVRP-capable devices send their updates to a
well-known multicast address and all GVRP-capable devices listen to this
address for information changes.
Enabling GVRP allows the Multilayer Switching Module dynamically
adjust active network topologies in response to configuration changes in
one or more VLANs. GVRP then advertises VLAN changes on each bridge
to all other GVRP bridges in the network.
Important Considerations
To use GVRP, consider the following:
■
You must explicitly enable GVRP as an entire bridge state and then as
an individual bridge port state for the appropriate ports (see
Chapter 9) to take advantage of dynamic IEEE 802.1Q VLAN
configuration. By default, GVRP is disabled as both a bridge state and
a bridge port state. If GVRP is enabled, the VLAN origin for a
port-based VLAN is dynamic (with GVRP). When GVRP is disabled, the
VLAN origin is either static (traditional static VLAN without GVRP) or
router (router port).