62CHAPTER 3: VLAN CONFIGURATION

join message. When the GARP participant wants to remove its attribute information from other switches, it sends a leave message. The leaveall timer is started at the same time that each GARP participant is enabled and a leaveall message is sent out when the leaveall timer times out. The join and leave messages cooperate to ensure the logout and the re-registration of a message. By exchanging messages, all the attribute information to be registered can be propagated to all the switches in the same switching network.

The destination MAC addresses of the packets of the GARP participants are specific multicast MAC addresses. A switch that supports GARP classifies the packets that it receives from GARP participants and processes them with the corresponding GARP applications (GVRP or GMRP).

GARP and GMRP are described in details in the IEEE 802.1p standard. The Switch 7750 fully supports GARP compliant with the IEEE standards.

The value of the GARP timer is used in all GARP applications, including GVRP and GMRP, that are running in a switching network.

In one switching network, GARP timers on all the switching devices should be set to the same value.

Setting the GARP Timers

GARP timers include the hold, join, and leaveall timers.

The GARP participant sends join message regularly when the join timer times out so that other GARP participants can register its attribute values.

When the GARP participant wants to remove attribute values, it sends a leave message. When the leave message arrives, the receiving GARP participant starts the leave timer. If the receiving participant does not receive a join message from the sender before the leave timer expires, the receiving participant removes the sender’s GARP attribute values.

The leaveall timer is started as soon as a GARP participant is enabled. A leaveall message is sent at timeout so that other GARP participants remove all the attribute values of this participant. Then, the leaveall timer is restarted and a new cycle begins.

When a switch receives GARP registration information, it does not send a join message immediately. Instead, it enables a hold timer and sends the join message outward when the hold timer times out. In this way, all the VLAN registration information received within the time specified by the hold timer can be sent in one frame to save bandwidth.

Table 56 Setting the GARP Timers

OperationCommand

Configure the hold, join, and leave timers in Ethernet port view.

Set the GARP hold, join, and garp timer { hold join leave } timer_value leave timers

Restore the default GARP undo garp timer { hold join leave } hold, join, and leave timer

settings

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3Com 10014298 manual Setting the Garp Timers