H3C Technologies H3C WX5500E Series Access Controllers - Manual (Page 171)

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When a GARP application is enabled, it starts a LeaveAll timer. The GARP participant sends a
LeaveAll message when the timer expires. Then, the LeaveAll timer restarts to begin a new cycle.
The LeaveAll timer and all other GARP timers also restart when the GARP participant receives a
LeaveAll message.
When you set the GARP timers, follow these guidelines:
• The settings of GARP timers apply to all GARP applications, such as GVRP, on a LAN.
• On a GARP-enabled network, each port maintains its own Hold, Join, and Leave timers, but only
one LeaveAll timer is maintained on each device. This LeaveAll timer applies to all ports on the
device.
• The value ranges for the Hold, Join, Leave, and LeaveAll timers are dependent on one another.
See
Table 19 for their dependencies.
• Set the LeaveAll timer greater than any Leave timer and not smaller than its default value, 1000
centiseconds. Each time a LeaveAll timer expires, a network-wide re-join occurs.
• A device may send LeaveAll messages at the interval set by its LeaveAll timer or the LeaveAll timer
on another device on the network, whichever is smaller. This is because each time a device on the
network receives a LeaveAll message it resets its LeaveAll timer.
GARP PDU format
As shown in Figure 49 , GARP PDUs are encapsulated in IEEE 802.3 Ethernet frames.
Figure 49 GARP PDU format
Table 18 describes the usage and values of fields contained in the GARP PDU portion of the Ethernet
frame.
Table 18 GARP PDU fields
Field Description Value
Protocol ID Protocol identifier for GARP. 0x0001.
Message
One or multiple messages, each containing
an attribute type and an attribute list.
N/A
End mark Indicates the end of a GARP PDU. 0x00.
Ethernet frame
Attribute length Attribute event Attribute value
DA SA Length DSAP SSAP Ctrl GARP PDU
Attribute list Attribute type
... Message n Message 1 Protocol ID End mark
... Attribute 1 Attribute n End mark