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Figure 113. VLAN Stacking without L2PT
You might need to transport control traffic transparently through the intermediate network to the other region. Layer 2 protocol
tunneling enables BPDUs to traverse the intermediate network by identifying frames with the Bridge Group Address, rewriting
the destination MAC to a user-configured non-reserved address, and forwarding the frames. Because the frames now use a
unique MAC address, BPDUs are treated as normal data frames by the switches in the intermediate network core. On egress
edge of the intermediate network, the MAC address rewritten to the original MAC address and forwarded to the opposing
network region (shown in the following illustration).
Dell Networking OS Behavior: In the Dell Networking OS versions prior to 8.2.1.0, the MAC address that Dell Networking
systems use to overwrite the Bridge Group Address on ingress was non-configurable. The value of the L2PT MAC address
was the Dell Networking-unique MAC address, 01-01-e8-00-00-00. As such, with these versions, Dell Networking systems are
required at the egress edge of the intermediate network because only the Dell Networking OS could recognize the significance
of the destination MAC address and rewrite it to the original Bridge Group Address. In the Dell Networking OS version 8.2.1.0
and later, the L2PT MAC address is user-configurable, so you can specify an address that non-Dell Networking systems can
recognize and rewrite the address at egress edge.
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Service Provider Bridging