Brocade Communications Systems Brocate Ethernet Access Switch 6910 - Manual (Page 770)

720 Brocade 6910 Ethernet Access Switch Configuration Guide
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IEEE 802.1Q VLANs
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• End stations can belong to multiple VLANs
• Passing traffic between VLAN-aware and VLAN-unaware devices
• Priority tagging
Assigning Ports to VLANs
Before enabling VLANs for the switch, you must first assign each port to the VLAN group(s) in which
it will participate. By default all ports are assigned to VLAN 1 as untagged ports. Add a port as a
tagged port if you want it to carry traffic for one or more VLANs, and any intermediate network
devices or the host at the other end of the connection supports VLANs. Then assign ports on the
other VLAN-aware network devices along the path that will carry this traffic to the same VLAN(s),
either manually or dynamically using GVRP. However, if you want a port on this switch to participate
in one or more VLANs, but none of the intermediate network devices nor the host at the other end
of the connection supports VLANs, then you should add this port to the VLAN as an untagged port.
NOTE
VLAN-tagged frames can pass through VLAN-aware or VLAN-unaware network interconnection
devices, but the VLAN tags should be stripped off before passing it on to any end-node host that
does not support VLAN tagging.
FIGURE 73 VLAN Compliant and VLAN Non-compliant Devices
VLAN Classification – When the switch receives a frame, it classifies the frame in one of two ways.
If the frame is untagged, the switch assigns the frame to an associated VLAN (based on the default
VLAN ID of the receiving port). But if the frame is tagged, the switch uses the tagged VLAN ID to
identify the port broadcast domain of the frame.
Port Overlapping – Port overlapping can be used to allow access to commonly shared network
resources among different VLAN groups, such as file servers or printers. Note that if you implement
VLANs which do not overlap, but still need to communicate, you can connect them by enabled
routing on this switch.
Untagged VLANs – Untagged VLANs are typically used to reduce broadcast traffic and to increase
security. A group of network users assigned to a VLAN form a broadcast domain that is separate
from other VLANs configured on the switch. Packets are forwarded only between ports that are
designated for the same VLAN. Untagged VLANs can be used to manually isolate user groups or
subnets. However, you should use IEEE 802.3 tagged VLANs with GVRP whenever possible to fully
automate VLAN registration.
VA
VA: VLAN Aware
VU: VLAN Unaware
VA
tagged frames
VA VU
VA
tagged
frames untagged
frames