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Figure 123. 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 EMC Networking OS Behavior: In Dell EMC Networking OS versions prior to 8.2.1.0, the MAC address that Dell EMC
Networking systems use to overwrite the Bridge Group Address on ingress was non-configurable. The value of the L2PT MAC
address was the Dell EMC Networking-unique MAC address, 01-01-e8-00-00-00. As such, with these Dell EMC Networking OS
versions, Dell EMC Networking systems are required at the egress edge of the intermediate network because only Dell EMC
Networking OS could recognize the significance of the destination MAC address and rewrite it to the original Bridge Group
Address. In Dell EMC 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 EMC Networking systems can recognize and rewrite the address at egress edge.
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Service Provider Bridging