VPLS Features
Page 256 7210 SAS-X, R6 OS Services Guide
BPDU Translation
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 and even if they are from the same vendor. In some
cases, it is necessary to provide BPDU translation in order to provide an interoperable e2e
solution.
To address these network designs, BPDU format translation is supported on devices. If enabled on
a given SAP, the system will intercept all BPDUs destined to that interface and perform required
format translation such as STP-to-PVST or vice versa.
Similarly, BPDU interception and redirection to the CPM is performed only at ingress meaning
that as soon as at least 1 port within a given VPLS service has BPDU translation enabled, all
BPDUs received on any of the VPLS ports will be redirected to the CPM.
BPDU translation involves all encapsulation actions that the data path would perform for a given
outgoing port (such as adding VLAN tags depending on the outer SAP 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 given VPLS
service.
L2PT and BPDU Translation
Tunnelling of Cisco Discovery Protocol (CDP), Digital Trunking Protocol (DTP), Port
Aggregation Protocol(PAGP), Uni-directional Link Detection (UDLD), Virtual Trunk Protocol
(VTP), STP (Spanning Tree Protocol) and PVST (per-VLAN Spanning Tree protocol) are
supported. These protocols automatically pass the other protocols tunneled by L2PT towards the
CPM and on tunnelling, all carry the same specific Cisco MAC.
Note: The CDP, DTP, PAGP, UDLD, VTP except STP and PVST is supported only on 7210 SAS-
R6.
The existing L2PT limitations apply.
• The protocols apply only to VPLS.
• The protocols are mutually exclusive with running STP on the same VPLS as soon as one
SAP has L2PT/BPDU translation enabled.
• Forwarding occurs on the CPM.
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