Virtual Private LAN Services
the egress U-PE for CMAC Y. In our example, B2 is assumed to be known as the B-DA for Y. If
CMAC Y is not present in the U-PE1 forwarding database, the PBB packet is sent in the B-VPLS
using the standard group MAC address for the ISID associated with the customer VPN.
Next, only the Backbone Header in green is used to switch the frame through the green B-VPLS/
VPLS instances in the N-PEs. At the receiving U-PE2, the CMAC X is learned as being behind
BMAC B1; then the PBB encapsulation is removed and the lookup for CMAC Y is performed.
7210 SAS M Services Guide
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