Virtual Private LAN Services
7750 SR OS Services Guide Page 777
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. If the
uplink to the N-PE is a spoke pseudowire, the related PWE3 encapsulation is added in front of the
B-DA.
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. In
the case where a pseudowire is used between N-PE and U-PE2, the pseudowire encapsulation is
removed first.
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