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GARP PDU format
Figure 45 GARP PDU format
As shown in Figure 45, GARP PDUs are encapsulated in IEEE 802.3 Ethernet frames.
Table 18 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)
Attribute event Event that the attribute describes
• 0x00—LeaveAll event
• 0x01—JoinEmpty event
• 0x02—JoinIn event
• 0x03—LeaveEmpty event
• 0x04—LeaveIn event
• 0x05—Empty event
Attribute value Attribute value
VLAN ID for GVRP
If the value of the attribute event field is
0x00 (LeaveAll event), the attribute value
field is invalid.
The destination MAC addresses of GARP messages are multicast MAC addresses, and vary with
GARP applications. For example, the destination MAC address of GVRP is 01-80-C2-00-00-21.
Ethernet frame
Attribute length Attribute event Attribute value
DA SA Length DSAP SSAP Ctrl GARP PDU
Attribute listAttribute type
... Message nMessage 1Protocol ID End mark
...Attribute 1 Attribute n End mark
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