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Configuring GARP/GVRP 43
attribute information by sending join declarations or withdrawal declarations. It
can also register or remove the attribute information of other GARP members
according to the join declarations or withdrawal declarations that it receives from
them.
GARP members exchange information by sending GARP messages. There are three
main types of GARP messages, including join, leave, and leaveall. When a GARP
participant wants to register its attribute information on other switches, it sends a
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 detail in the IEEE 802.1p standard. The Switch
8800 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 switched network.
■ In one switched 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 joins. 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