The generic attribute registration protocol (GARP), provides a mechanism that allows participants in a GARP application to distribute, propagate, and register with other participants in a bridged LAN the attributes specific to the GARP application, such as the VLAN or multicast attribute.

GARP itself does not exist on a device as an entity. GARP-compliant application entities are called GARP applications. One example is GVRP. When a GARP application entity is present on a port on your device, this port is regarded a GARP application entity.

GARP messages and timers

1) GARP messages

GARP members communicate with each other through the messages exchanged between them. The messages performing important functions for GARP fall into three types: Join, Leave and LeaveAll.

l When a GARP entity wants its attribute information to be registered on other devices, it sends Join messages to these devices. A GARP entity also sends Join messages when it receives Join messages from other entities or it wants some of its statically configured attributes to be registered on other GARP entities.

l When a GARP entity wants some of its attributes to be deregistered on other devices, it sends Leave messages to these devices. A GARP entity also sends Leave messages when it receives Leave messages from other entities for deregistering some attributes or it has some attributes statically deregistered.

l Once a GARP entity is launched, the LeaveAll timer is triggered at the same time. The GARP entity sends out LeaveAll messages after the timer times out. LeaveAll messages deregister all the attributes, through which the attribute information of the entity can be registered again on the other GARP entities.

Leave messages, LeaveAll messages, together with Join messages ensure attribute information can be deregistered and re-registered.

Through message exchange, all the attribute information to be registered can be propagated to all the GARP-enabled switches in the same LAN.

2) GARP timers

Timers determine the intervals of sending different types of GARP messages. GARP defines four timers to control the period of sending GARP messages.

l Hold: When a GARP entity 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 and puts all received registration information before the timer times out into one Join message and sends out the message after the timer times out.

l Join: To make sure the devices can receive Join messages, each Join message is sent twice. If the first Join message sent is not responded for a specific period, a second one is sent. The period is determined by this timer.

l Leave: When a GARP entity expects to deregister a piece of attribute information, it sends out a Leave message. Any GARP entity receiving this message starts its Leave timer, and deregisters the attribute information if it does not receives a Join message again before the timer times out.

l LeaveAll: Once a GARP entity starts up, it starts the LeaveAll timer, and sends out a LeaveALL message after the timer times out, so that other GARP entities can re-register all the attribute information on this entity. After that, the entity restarts the LeaveAll timer to begin a new cycle.

l The settings of GARP timers apply to all GARP applications, such as GVRP, on a LAN.

l Unlike other three timers, which are set on a port basis, the LeaveAll timer is set in system view and takes effect globally.

l A GARP application entity 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.

Operating mechanism of GARP

Through the mechanism of GARP, the configuration information on a GARP member will be propagated within the whole LAN. A GARP member can be a terminal workstation or a bridge; it instructs other GARP members to register/deregister its attribute information by declaration/recant, and register/deregister other GARP member's attribute information according to other member's declaration/recant. When a port receives an attribute declaration, the port will register this attribute. When a port receives an attribute recant, the port will deregister this attribute.

The protocol packets of GARP entities use specific multicast MAC addresses as their destination MAC addresses. When receiving these packets, the switch distinguishes them by their destination MAC addresses and delivers them to different GARP application (for example, GVRP) for further processing.

GARP message format

The GARP packets are in the following format:

Figure 1-1 Format of GARP packets

The following table describes the fields of a GARP packet.

Table 1-1 Description of GARP packet fields

Field	Description	Value
Protocol ID	Protocol ID	1
Message	Each message consists of two parts: Attribute Type and Attribute List.	—
Attribute Type	Defined by the specific GARP application	The attribute type of GVRP is 0x01.
Attribute List	It contains multiple attributes.	—
Attribute	Each general attribute consists of three parts: Attribute Length, Attribute Event, and Attribute Value. Each LeaveAll attribute consists of two parts: Attribute Length and LeaveAll Event.	—
Attribute Length	The length of the attribute	2 to 255 (in bytes)
Attribute Event	The event described by the attribute	0: LeaveAll Event 1: JoinEmpty 2: JoinIn 3: LeaveEmpty 4: LeaveIn 5: Empty
Attribute Value	The value of the attribute	For GVRP packets, the value of this field is the VLAN ID; however, for LeaveAll messages, this field is invalid.
End Mark	End mark of an GARP PDU	The value of this field is fixed to 0x00.

GVRP

As an implementation of GARP, GARP VLAN registration protocol (GVRP) maintains dynamic VLAN registration information and propagates the information to the other switches through GARP.

With GVRP enabled on a device, the VLAN registration information received by the device from other devices is used to dynamically update the local VLAN registration information, including the information about the VLAN members, the ports through which the VLAN members can be reached, and so on. The device also propagates the local VLAN registration information to other devices so that all the devices in the same LAN can have the same VLAN information. VLAN registration information propagated by GVRP includes static VLAN registration information, which is manually configured locally on each device, and dynamic VLAN registration information, which is received from other devices.

GVRP has the following three port registration modes: Normal, Fixed, and Forbidden, as described in the following.

l Normal. A port in this mode can dynamically register/deregister VLANs and propagate dynamic/static VLAN information.

l Fixed. A port in this mode cannot register/deregister VLANs dynamically. It only propagates static VLAN information. Besides, the port permits only static VLANs, that is, it propagates only static VLAN information to the other GARP members.

l Forbidden. A port in this mode cannot register/deregister VLANs dynamically. It permits only the default VLAN (namely, VLAN 1), that is, the port propagates only the information about VLAN 1 to the other GARP members.

Protocol Specifications

GVRP is defined in IEEE 802.1Q standard.

GVRP Configuration

GVRP Configuration Tasks

Complete the following tasks to configure GVRP:

Task	Remarks
Enabling GVRP	Required
Configuring GVRP Timers	Optional
Configuring GVRP Port Registration Mode	Optional

Enabling GVRP

Configuration Prerequisite

The port on which GVRP will be enabled must be set to a trunk port.

Configuration procedure

Follow these steps to enable GVRP:

To do ...	Use the command ...	Remarks
Enter system view	system-view	—
Enable GVRP globally	gvrp	Required By default, GVRP is disabled globally.
Enter Ethernet port view	interface interface-type interface-number	—
Enable GVRP on the port	gvrp	Required By default, GVRP is disabled on the port.

l After you enable GVRP on a trunk port, you cannot change the port to a different type.

l Use the port trunk permit all command to permit the traffic of all dynamically registered VLANs to pass through a trunk port with GVRP enabled.

Configuring GVRP Timers

Follow these steps to configure GVRP timers:

To do ...	Use the command ...	Remarks
Enter system view	system-view	—
Configure the LeaveAll timer	garp timer leaveall timer-value	Optional By default, the LeaveAll timer is set to 1,000 centiseconds.
Enter Ethernet port view	interface interface-type interface-number	—
Configure the Hold, Join, and Leave timers	garp timer { hold \| join \| leave } timer-value	Optional By default, the Hold, Join, and Leave timers are set to 10, 20, and 60 centiseconds respectively.

Note that:

l The setting of each timer must be a multiple of 5 (in centiseconds).

l The timeout ranges of the timers vary depending on the timeout values you set for other timers. If you want to set the timeout time of a timer to a value out of the current range, you can set the timeout time of the associated timer to another value to change the timeout range of this timer.

The following table describes the relations between the timers:

Table 1-2 Relations between the timers

Timer	Lower threshold	Upper threshold
Hold	10 centiseconds	This upper threshold is less than or equal to one-half of the timeout time of the Join timer. You can change the threshold by changing the timeout time of the Join timer.
Join	This lower threshold is greater than or equal to twice the timeout time of the Hold timer. You can change the threshold by changing the timeout time of the Hold timer.	This upper threshold is less than one-half of the timeout time of the Leave timer. You can change the threshold by changing the timeout time of the Leave timer.
Leave	This lower threshold is greater than twice the timeout time of the Join timer. You can change the threshold by changing the timeout time of the Join timer.	This upper threshold is less than the timeout time of the LeaveAll timer. You can change the threshold by changing the timeout time of the LeaveAll timer.
LeaveAll	This lower threshold is greater than the timeout time of the Leave timer. You can change threshold by changing the timeout time of the Leave timer.	32,765 centiseconds

The following are recommended GVRP timer settings:

l GARP hold timer: 100 centiseconds (1 second)

l GARP Join timer: 600 centiseconds (6 seconds)

l GARP Leave timer: 3000 centiseconds (30 seconds)

l GARP LeaveAll timer: 120000 centiseconds (2 minutes)

Configuring GVRP Port Registration Mode

Follow these steps to configure GVRP port registration mode:

To do ...	Use the command ...	Remarks
Enter system view	system-view	—
Enter Ethernet port view	interface interface-type interface-number	—
Configure GVRP port registration mode	gvrp registration { fixed \| forbidden \| normal }	Optional By default, GVRP port registration mode is normal.

Displaying and Maintaining GVRP

To do …	Use the command …	Remarks
Display GARP statistics	display garp statistics [ interface interface-list ]	Available in any view
Display the settings of the GARP timers	display garp timer [ interface interface-list ]
Display GVRP statistics	display gvrp statistics [ interface interface-list ]
Display the global GVRP status	display gvrp status
Clear GARP statistics	reset garp statistics [ interface interface-list ]

GVRP Configuration Example

Network requirements

l Enable GVRP on all the switches in the network so that the VLAN configurations on Switch C and Switch E can be applied to all switches in the network, thus implementing dynamic VLAN information registration and refresh.

l By configuring the GVRP registration modes of specific Ethernet ports, you can enable the corresponding VLANs in the switched network to communicate with each other.

Network diagram

Figure 1-2 Network diagram for GVRP configuration

Configuration procedure

1) Configure Switch A

# Enable GVRP globally.

<SwitchA> system-view

[SwitchA] gvrp

# Configure Ethernet1/0/1 to be a trunk port and to permit the packets of all the VLANs.

[SwitchA] interface Ethernet 1/0/1

[SwitchA-Ethernet1/0/1] port link-type trunk

[SwitchA-Ethernet1/0/1] port trunk permit vlan all

# Enable GVRP on Ethernet1/0/1.

[SwitchA-Ethernet1/0/1] gvrp

[SwitchA-Ethernet1/0/1] quit

# Configure Ethernet1/0/2 to be a trunk port and to permit the packets of all the VLANs.

[SwitchA] interface Ethernet 1/0/2

[SwitchA-Ethernet1/0/2] port link-type trunk

[SwitchA-Ethernet1/0/2] port trunk permit vlan all

# Enable GVRP on Ethernet1/0/2.

[SwitchA-Ethernet1/0/2] gvrp

[SwitchA-Ethernet1/0/2] quit

# Configure Ethernet1/0/3 to be a trunk port and to permit the packets of all the VLANs.

[SwitchA] interface Ethernet 1/0/3

[SwitchA-Ethernet1/0/3] port link-type trunk

[SwitchA-Ethernet1/0/3] port trunk permit vlan all

# Enable GVRP on Ethernet1/0/3.

[SwitchA-Ethernet1/0/3] gvrp

[SwitchA-Ethernet1/0/3] quit

2) Configure Switch B

# The configuration procedure of Switch B is similar to that of Switch A and is thus omitted.

3) Configure Switch C

# Enable GVRP on Switch C, which is similar to that of Switch A and is thus omitted.

# Create VLAN 5.

[SwitchC] vlan 5

[SwitchC-vlan5] quit

4) Configure Switch D

# Enable GVRP on Switch D, which is similar to that of Switch A and is thus omitted.

# Create VLAN 8.

[SwitchD] vlan 8

[SwitchD-vlan8] quit

5) Configure Switch E

# Enable GVRP on Switch E, which is similar to that of Switch A and is thus omitted.

# Create VLAN 5 and VLAN 7.

[SwitchE] vlan 5

[SwitchE-vlan5] quit

[SwitchE] vlan 7

[SwitchE-vlan7] quit

6) Display the VLAN information dynamically registered on Switch A, Switch B, and Switch E.

# Display the VLAN information dynamically registered on Switch A.

[SwitchA] display vlan dynamic

Total 3 dynamic VLAN exist(s).

The following dynamic VLANs exist:

5, 7, 8,

# Display the VLAN information dynamically registered on Switch B.

[SwitchB] display vlan dynamic

Total 3 dynamic VLAN exist(s).

The following dynamic VLANs exist:

5, 7, 8,

# Display the VLAN information dynamically registered on Switch E.

[SwitchE] display vlan dynamic

Total 1 dynamic VLAN exist(s).

The following dynamic VLANs exist:

7) Configure Ethernet1/0/1 on Switch E to operate in fixed GVRP registration mode and display the VLAN information dynamically registered on Switch A, Switch B, and Switch E.

# Configure Ethernet1/0/1 on Switch E to operate in fixed GVRP registration mode.

[SwitchE] interface Ethernet 1/0/1

[SwitchE-Ethernet1/0/1] gvrp registration fixed

# Display the VLAN information dynamically registered on Switch A.

[SwitchA] display vlan dynamic

Total 3 dynamic VLAN exist(s).

The following dynamic VLANs exist:

5, 7, 8,

# Display the VLAN information dynamically registered on Switch B.

[SwitchB] display vlan dynamic

Total 3 dynamic VLAN exist(s).

The following dynamic VLANs exist:

5, 7, 8,

# Display the VLAN information dynamically registered on Switch E.

[SwitchE-Ethernet1/0/1] display vlan dynamic

No dynamic vlans exist!

8) Configure Ethernet1/0/1 on Switch E to operate in forbidden GVRP registration mode and display the VLAN registration information dynamically registered on Switch A, Switch B, and Switch E.

# Configure Ethernet1/0/1 on Switch E to operate in forbidden GVRP registration mode.

[SwitchE-Ethernet1/0/1] gvrp registration forbidden

# Display the VLAN information dynamically registered on Switch A.

[SwitchA] display vlan dynamic

Total 2 dynamic VLAN exist(s).

The following dynamic VLANs exist:

5, 8,

# Display the VLAN information dynamically registered on Switch B.

[SwitchB] display vlan dynamic

Total 2 dynamic VLAN exist(s).

The following dynamic VLANs exist:

5, 8,

# Display the VLAN information dynamically registered on Switch E.

[SwitchE] display vlan dynamic

No dynamic vlans exist!

H3C S3600 Operation Manual-Release 1602(V1.02)

GARP messages and timers

Operating mechanism of GARP

GARP message format

Configuration Prerequisite

Configuration procedure

Displaying and Maintaining GVRP

Network requirements

Network diagram

Configuration procedure

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