Figure 74 – Brocade Communications Systems Brocate Ethernet Access Switch 6910 User Manual
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Brocade 6910 Ethernet Access Switch Configuration Guide
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IEEE 802.1Q VLANs
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Automatic VLAN Registration – GVRP (GARP VLAN Registration Protocol) defines a system whereby
the switch can automatically learn the VLANs to which each end station should be assigned. If an
end station (or its network adapter) supports the IEEE 802.1Q VLAN protocol, it can be configured
to broadcast a message to your network indicating the VLAN groups it wants to join. When this
switch receives these messages, it will automatically place the receiving port in the specified
VLANs, and then forward the message to all other ports. When the message arrives at another
switch that supports GVRP, it will also place the receiving port in the specified VLANs, and pass the
message on to all other ports. VLAN requirements are propagated in this way throughout the
network. This allows GVRP-compliant devices to be automatically configured for VLAN groups based
solely on end station requests.
To implement GVRP in a network, first add the host devices to the required VLANs (using the
operating system or other application software), so that these VLANs can be propagated onto the
network. For both the edge switches attached directly to these hosts, and core switches in the
network, enable GVRP on the links between these devices. You should also determine security
boundaries in the network and disable GVRP on the boundary ports to prevent advertisements
from being propagated, or forbid those ports from joining restricted VLANs.
NOTE
If you have host devices that do not support GVRP, you should configure static or untagged VLANs
for the switch ports connected to these devices (as described in
“Adding Static Members to VLANs”
). But you can still enable GVRP on these edge switches, as well as on the core switches
in the network.
FIGURE 74
Using GVRP
Forwarding Tagged/Untagged Frames
If you want to create a small port-based VLAN for devices attached directly to a single switch, you
can assign ports to the same untagged VLAN. However, to participate in a VLAN group that crosses
several switches, you should create a VLAN for that group and enable tagging on all ports.
Ports can be assigned to multiple tagged or untagged VLANs. Each port on the switch is therefore
capable of passing tagged or untagged frames. When forwarding a frame from this switch along a
path that contains any VLAN-aware devices, the switch should include VLAN tags. When forwarding
a frame from this switch along a path that does not contain any VLAN-aware devices (including the
destination host), the switch must first strip off the VLAN tag before forwarding the frame. When
the switch receives a tagged frame, it will pass this frame onto the VLAN(s) indicated by the frame
tag. However, when this switch receives an untagged frame from a VLAN-unaware device, it first
decides where to forward the frame, and then inserts a VLAN tag reflecting the ingress port’s
default VID.
Port-based VLAN
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