348 BigIron RX Series Configuration Guide
53-1002253-01
SuperSpan™
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FIGURE 34 SuperSpan example
In this example, the SP network contains two devices that are running SuperSpan. The SP is
connected to two customer networks. Each customer network is running its own instance of STP.
SuperSpan prevents Layer 2 loops in the traffic flow with each customer while at the same time
isolating each customer’s traffic and spanning tree from the traffic and spanning trees of other
customers. For example, the SP devices provide loop prevention for Customer 1 while ensuring
that Customer 1’s traffic is never forwarded to Customer 2. In this example, customer 1 has two
interfaces to the SP network, ports 1/1 and 1/2 connected to SP 1. The SP network behaves like a
non-blocking hub. BPDUs are tunneled through the network. To prevent a Layer 2 loop, customer
1’s port 1/2 enters the blocking state.
Customer ID
SuperSpan uses a SuperSpan customer ID to uniquely identify and forward traffic for each
customer. You assign the customer ID as part of the SuperSpan configuration of the Brocade
devices in the SP. In Table 34 on page 348, the spanning trees of customer 1 and customer 2 do
not interfere with one another because the SP network isolates each customer’s spanning tree
based on the SuperSpan customer IDs in the traffic.
BPDU forwarding
When a Brocade device receives a customer's BPDU on a boundary interface, the device changes
the destination MAC address of the BPDU from the bridge group address (01-80-c2-00-00-00) as
follows.
The first byte (locally administered bit) is changed from 01 to 03, to indicate that the BPDU needs
to be tunneled.
The fourth and fifth bytes are changed to the customer STP ID specified on the boundary interface.
For example, if the customer's STP ID is 1, the destination MAC address of the customer's BPDUs is
changed to the following: 03-80-c2-00-01-00.
Cust 1
Cust 2
Port1/2
Port1/2
Port1/1
Port1/1
Port1/1
FWD
FWD
BLK
BLK
Port1/2
Port2/1
Port2/2
SuperSpan
root bridge
SP 1
SP 2
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