VPLS networks are typically used to interconnect different customer sites using different access technologies such as Ethernet and bridged-encapsulated ATM PVCs. Typically, different Layer 2 devices can support different types of STP, even if they are from the same vendor. In some cases, it is necessary to provide BPDU translation to provide an interoperable e2e solution.
To address these network designs, BPDU format translation is supported on 7450 ESS, 7750 SR, and 7950 XRS devices. If enabled on a specified SAP or spoke-SDP, the system intercepts all BPDUs destined for that interface and perform required format translation such as STP-to-PVST or the other way around.
Similarly, BPDU interception and redirection to the CPM is performed only at ingress, meaning that as soon as at least one port within a specified VPLS service has BPDU translation enabled, all BPDUs received on any of the VPLS ports are redirected to the CPM.
BPDU translation requires all encapsulation actions that the data path would perform for a specified outgoing port (such as adding VLAN tags depending on the outer SAP and the SDP encapsulation type) and adding or removing all the required VLAN information in a BPDU payload.
This feature can be enabled on a SAP only if STP is disabled in the context of the specified VPLS service.