SPB VSI
An SPB virtual switch instance (SPB VSI) provides MAC-in-MAC tunnel service for Ethernet service instances. An SPB VSI acts as a virtual switch. It has all the functionality of a conventional Ethernet switch, including source MAC address learning, MAC address aging, and flooding. Each SPB VSI is uniquely identified by an I-SID. For more information about VSIs, see VPLS in MPLS Configuration Guide.