18 GVRP CONFIGURATIONIntroduction to GARPand GVRPIntroduction to GARP GARP (generic attribute registration protocol) offers a mechanism that is used bythe members in the same switching network to distribute, propagate and registersuch information as VLAN and multicast addresses.GARP dose not exist in a switch as an entity. A GARP participant is called GARPapplication. The main GARP applications at present are GVRP and GMRP. GVRP isdescribed in the “GVRP Mechanism” on page 154 and GMRP will be described inMulticast Configuration. When a GARP participant is on a port of the switch, eachport corresponds to a GARP participant.Through GARP mechanism, the configuration information on one GARP memberwill be advertised rapidly in the whole switching network. GARP member can be aterminal workstation or bridge. A GARP member can notify other members toregister or remove its attribute information by sending declarations or withdrawaldeclarations. It can also register or remove the attribute information of otherGARP members according to the received declarations/withdrawal declarations.GARP members exchange information through sending messages. There mainlyare 3 types of GARP messages including Join, Leave, and LeaveAll.■ When a GARP participant wants to register its attribute information on otherswitches, it will send Join message outward.■ When it wants to remove some attribute values from other switches, it willsend Leave message.■ LeaveAll timer will be started at the same time when each GARP participant isenabled and LeaveAll message will be sent upon timeout.Leave message and LeaveAll message cooperate to ensure the logout and there-registration of a message. Through exchanging messages, all the attributeinformation to be registered can be propagated to all the switches in the sameswitching network.The destination MAC addresses of the packets of the GARP participants arespecific multicast MAC addresses. A GARP-supporting switch will classify thepackets received from the GARP participants and process them withcorresponding GARP applications (GVRP or GMRP).GARP and GMRP are described in details in the IEEE 802.1p standard (which hasbeen added to the IEEE802.1D standard). 3Com Series Ethernet Switches fullysupport the GARP compliant with the IEEE standards.
