173
•
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
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 can send LeaveAll messages at the interval set by its LeaveAll timer or the LeaveAll timer
of 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
Figure 58
GARP PDU format
As shown in
, GARP PDUs are encapsulated in IEEE 802.3 Ethernet frames.
Table 19
GARP PDU fields
Field Description
Value
Protocol ID
Protocol identifier for GARP
0x0001
Message
One or multiple messages, each of which
contains an attribute type and an attribute
list
N/A
End mark
Indicates the end of a GARP PDU
0x00
Attribute type
Defined by the GARP application
0x01 for GVRP, which indicates the VLAN
ID attribute
Attribute list
Contains one or multiple attributes
N/A
Attribute
Consists of an attribute length, an attribute
event, and an attribute value
N/A
Attribute length
Length of an attribute, inclusive of the
attribute length field
2 to 255 (in bytes)
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
