Enterasys Networks D-Series - Manual (Page 292)

Enabling/Disabling GVRP (GARP VLAN Registration Protocol)
9-20 802.1Q VLAN Configuration
Enabling/Disabling GVRP (GARP VLAN Registration Protocol)
About GARP VLAN Registration Protocol (GVRP)
The following sections describe the device operation when its ports are operating under the
Generic Attribute Registration Protocol (GARP) application – GARP VLAN Registration Protocol
(GVRP).
Overview
The purpose of GVRP is to dynamically create VLANs across a switched network. When a VLAN
is declared, the information is transmitted out GVRP configured ports on the device in a GARP
formatted frame using the GVRP multicast MAC address. A switch that receives this frame,
examines the frame, and extracts the VLAN IDs. GVRP then creates the VLANs and adds the
receiving port to its tagged member list for the extracted VLAN ID (s). The information is then
transmitted out the other GVRP configured ports of the device.
Figure 9‐1 shows an example of
how VLAN blue from end station A would be propagated across a switch network.
How It Works
In Figure 9‐1 on page 9‐21, Switch 4, port 1 is registered as being a member of VLAN Blue and
then declares this fact out all its ports (2 and 3) to Switch 1 and Switch 2. These two devices
register this in the port egress lists of the ports (Switch 1, port 1 and Switch 2, port 1) that received
the frames with the information. Switch 2, which is connected to Switch 3 and Switch 5 declares
the same information to those two devices and the port egress list of each port is updated with the
new information, accordingly.
Configuring a VLAN on an 802.1Q switch creates a static VLAN entry. The entry will always
remain registered and will not time out. However, dynamic entries will time‐out and their
registrations will be removed from the member list if the end station A is removed. This ensures
that, if switches are disconnected or if end stations are removed, the registered information
remains accurate.
The end result is that the port egress list of a port is updated with information about VLANs that
reside on that port, even if the actual station on the VLAN is several hops away.