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Field Description Value
Attribute
Consists of an Attribute Length, an
Attribute Event, and an Attribute
Value
––
Attribute length
Length of an attribute, inclusive of
the attribute length field
2 to 255 (in bytes)
Attribute event Event described by the attribute
• 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. A switch
distributes GARP messages to different GARP applications according to the destination MAC addresses
carried in GARP messages.
GVRP
GVRP overview
As a GARP application, GVRP enables a switch to propagate local VLAN registration information to other
participant devices and dynamically update the VLAN registration information from other devices to its
local database about active VLAN members and through which port they can be reached. Thus, it
ensures that all GVRP participants on a bridged LAN maintain the same VLAN registration information.
The VLAN registration information propagated by GVRP includes both manually configured local static
entries and dynamic entries from other devices.
GVRP registration modes
VLANs manually created are called static VLANs, and VLANs created by GVRP are called dynamic
VLANs. GVRP provides the following registration modes on a port, including Normal, Fixed, and
Forbidden. In different registration modes, a port handles static and dynamic VLANs differently.
• Normal––Allows dynamic creation, registration, and deregistration of VLANs on the trunk port.
• Fixed––Allows manual creation and registration of VLANs, prevents VLAN deregistration, and
registers all known VLANs on other ports on the trunk port.
• Forbidden––Deregisters all VLANs (except VLAN 1) and prevents any further VLAN creation or
registration on the trunk port.
Protocols and standards
• IEEE 802.1Q, Virtual Bridged Local Area Networks
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