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Generic Attribute Registration Protocol (GARP) A-1
A
Generic Attribute Registration Protocol
(GARP)
This appendix describes the switch operation when its ports are operating under the Generic
Attribute Registration Protocol (GARP) application – GARP VLAN Registration Protocol
(GVRP).
A.1 OVERVIEW
The process of the forwarding decision and tagging frames is the same as for 802.1Q as described
in Chapter 12. However, the GVRP protocol frames will not have a tag even when transmitted out
an 802.1Q Trunk Port.
The purpose of GVRP is to dynamically create VLANs across a switched network. When a VLAN
is declared, the information is transmitted out GVRP configured ports on the switch in a GARP
formatted frame using the GVRP multicast MAC address. A switch that receives this frame,
examines the frame, and extracts the VLAN IDs. GVRP then creates the VLANs and adds the
receiving port to its tagged member list for the extracted VLAN ID(s). The information is then
transmitted out the other GVRP configured ports of the switch. Figure A-1 shows an example of
how VLAN blue from end station A would be propagated across a switch network.
NOTE: There is a global setting for GVRP that is enabled by default. Access to these
settings is only available through a MIB.