3Com Switch 7754, Configuration Manual

Page: 154 / 940

154 C
HAPTER
18: GVRP C
ONFIGURATION
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The value of GARP timer will be used in all the GARP applications, including
GVRP and GMRP, running in one switching network.
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In one switching network, the GARP timers on all the switching devices should
be set to the same value. Otherwise, GARP application cannot work normally.
GVRP Mechanism GARP Timers
GARP timers include Hold timer, Join timer, Leave timer and LeaveAll timer.
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Hold: When a GARP participant 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.
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Join: To transmit the Join messages reliably to other entities, a GARP participant
sends each Join message two times. The Join timer is used to define the interval
between the two sending operations of each Join message.
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Leave: When a GARP participant expects to unregister a piece of attribute
information, it sends out a Leave message. Any GARP participant receiving this
message starts its Leave timer, and unregisters the attribute information if it
does not receives a Join message again before the timer times out.
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LeaveAll: Once a GARP participant starts up, it starts the LeaveAll timer, and
sends out a LeaveALL message after the timer times out, so that other GARP
participants can re-register all the attribute information on this participant.
After that, the participant restarts the LeaveAll timer to begin a new cycle.
GVRP port registration mode
GVRP has the following three port registration modes: Normal, Fixed, and
Forbidden.
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Normal: In this mode, a port can dynamically register/deregister a VLAN and
propagate the dynamic/static VLAN information.
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Fixed: In this mode, a port cannot register/deregister a VLAN dynamically. It
only propagates static VLAN information. That is, a trunk port only permits the
packets of manually configured VLANs in this mode even if you configure the
port to permit the packets of all the VLANs.
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Forbidden: In this mode, a port cannot register/deregister VLANs. It only
propagates VLAN 1 information. That is, a trunk port only permits the packets
of the default VLAN (namely VLAN 1) in this mode even if you configure the
port to permit the packets of all the VLANs.
GARP operation procedure
Through the mechanism of GARP, the configuration information on a GARP
member will be propagated to the entire switched network. A GARP can be a
terminal workstation or a bridge; it instructs other GARP member to
register/unregister its attribute information by declaration/recant, and
register/unregister other GARP member’s attribute information according to other
member’s declaration/recant.
The protocol packets of GARP entity use specific multicast MAC addresses as their
destination MAC addresses. When receiving these packets, the switch