3Com Switch 4200G Configuration Guide

GVRP CONFIGURATION

Introduction to GVRP GVRP (GARP VLAN registration protocol) is an application of GARP (generic attribute

registration protocol). GVRP is based on the mechanism of GARP; it maintains

dynamic VLAN registration information and propagates the information to other

switches.

GARP is a generic attribute registration protocol. This protocol provides a mechanism

for the switching members in a switched network to register, distribute and

propagate information about VLANs, multicast addresses, and so on between each

other.

After the GVRP feature is enabled on a switch, the switch can receive the VLAN

registration information from other switches to dynamically update the local VLAN

registration information (including current VLAN members, which ports these VLAN

members get to, and so on), and propagate the local VLAN registration information

to other switches so that all the switching devices in the same switched network can

have the same VLAN information. The VLAN registration information includes not

only the static registration information configured locally, but also the dynamic

registration information from other switches.

GVRP Mechanism GARP Timers

The information exchange between GARP members is completed by messages. The

messages performing important functions for GARP fall into three types: Join, Leave

and LeaveAll.

■ When a GARP entity expects other switches to register certain attribute

information of its own, it sends out a Join message.

■ When a GARP entity expects other switches to unregister certain attribute

information of its own, it sends out a Leave message.

■ Once a GARP entity starts up, it starts the LeaveAll timer. After the timer times out,

the GARP entity sends out a LeaveAll message.

The join message and the Leave message are used together to complete the

unregistration and re-registration of information. Through message exchange, all the

attribute information to be registered can be propagated to all the switches in the

same switched network.

GARP has the following timers:

■ Hold: When a GARP entity receives a piece of registration information, it does not

send out a Join message immediately. Instead, to save the bandwidth resources, it

starts the Hold timer, puts all registration information it receives before the timer

times out into one Join message and sends out the message after the timer times

out.

■ Join: To transmit the Join messages reliably to other entities, a GARP entity sends

each Join message two times. The Join timer is used to define the interval between

the two sending operations of each Join message.

■ Leave: When a GARP entity expects to unregister a piece of attribute information,

it sends out a Leave message. Any GARP entity receiving this message starts its