Allied Telesis AT-S63 User Manual

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AT-S63 Management Software Features Guide
Section VI: Virtual LANs
263
Overview
The GARP VLAN Registration Protocol (GVRP) allows network devices to 
share VLAN information. The main purpose of GVRP is to allow switches 
to automatically discover some of the VLAN information that would 
otherwise need to be manually configured in each switch. This is helpful in 
networks where VLANs span more than one switch. Without GVRP, you 
must manually configure your switches to ensure that the various parts of 
a VLAN can communicate across the different switches. GVRP, which is 
an application of the Generic Attribute Registration Protocol (GARP), does 
this for you automatically.
The AT-S63 Management Software uses GVRP protocol data units 
(PDUs) to share VLAN information among GVRP-active devices. The 
PDUs contain the VID numbers of the VLANs on the switch. A PDU 
contains the VIDs of all the VLANs on the switch, not just the VID of which 
the transmitting port is a member.
When a switch receives a GVRP PDU on a port, it examines the PDU to 
determine the VIDs of the VLANs on the device that sent it. It then does 
the following:
ˆ
If a VLAN does not exist on the switch, it creates the VLAN and adds 
the port as a tagged member to the VLAN. A VLAN created by GVRP 
is called a dynamic GVRP VLAN
ˆ
If the VLAN already exists on the switch but the port is not a member of 
it, the switch adds the port as a tagged member. A port that has been 
added by GVRP to a static VLAN (that is a user-created VLAN) is 
called a dynamic GVRP port.
You cannot modify a dynamic GVRP VLAN. After it is created, only GVRP 
can modify or delete it. A dynamic GVRP VLAN exists only so long as 
there are active nodes in the network that belong to the VLAN. If all nodes 
of a dynamic GVRP VLAN are shut down and there are no active links, the 
VLAN is deleted from the switch.
A dynamic GVRP port in a static VLAN remains a member of the VLAN as 
long as there are active VLAN members. If all members of the VLAN 
become inactive or there are no active links, GVRP removes the dynamic 
port from the VLAN, but does not delete the VLAN if the VLAN is a static 
VLAN.