Foundry NetIron M2404C and M2404F Metro Access Switches Configuring VLANs (Rev.03)
Super VLANs
© 2008 Foundry Networks, Inc.
Page 50 of 73
Super VLAN and MSTP fast ring features are configured on each device in the topology presented
in
Figure 11
. The Super VLAN uplink has to be one of the two ports that are connected to the rest
of the ring. Assume that one of the clients connected to switch D sends broadcast traffic, the traffic
will travel counterclockwise only, since the Super VLAN active uplink port is the root port. If a
link is disconnected between port B and A, a topology change occurs and switch D chooses a new
Super VLAN uplink port. As a result, after the cut the broadcast traffic flows clockwise only.
Dynamic Super VLAN occurs on all the bridges in
Figure 11
except for the root bridge since it
does not have a root port (only designated ports).
NOTE
The Super VLAN for ring topology can be enabled only if MSTP is enabled.
Use the
super-vlan ring-topology
command in Interface Configuration mode to set the ring-
topology Super VLAN.
VLAN Translation
Traffic between end users can be isolated by using an alternative method known as VLAN
translation. VLAN translation provides traffic to the user VLAN from more than one uplink port or
trunk, at the same time guaranteeing that communication between users remains impossible. For
example, Super VLAN ring mode allows traffic to the user to arrive only from the MSTP root port.
However, VLAN translation allows user ports to also receive traffic that is forwarded from the
MSTP designated port. VLAN translation is preferred in business-to-business communications,
where multiple servers pertaining to different VLANs (based on the end-user groups) are used.
As the packet enters the service provider’s network, the VLAN translation feature translates the
customer’s VLAN ID into a
transport VLAN ID
that is predefined by the service provider. By
simply mapping the transport VLAN ID to the customer packet and leaving the rest of this packet
untouched, the user’s QoS information can be preserved and honored as it traverses the service
provider’s network.
In MSTP topology the VLAN translation feature has the ability to force the user traffic to the root
port only. Thus, the traffic to the server is not forwarded to other ports.
Special measures are taken to perform additional MAC address learning via the configured VLAN
translation map.
Super VLAN Configuration Flow
Figure 12
displays the process to configure Super VLAN parameters.