Hello,
We're working on deploying some L2 services over an MPLS network. Our model includes a CPE with OAM capabilities and QinQ from the PE to the CPE. For now we want to do simple OAM functions from CPE-CPE (no MIPs in the MPLS network).
Our lab testing has shown some sort of incompatibilities between OAM and QinQ. OAM frames are encapsulated with a single VLAN tag (the SVLAN) on the CPE. When the PEs only perform SVLAN swapping, everything works fine. If we configure the PE to also perform CVLAN manipulation, it drops OAM frames. It likely does not know how to process them because they don't have a CVLAN tag. We're working with 2 CPE vendors and neither of them are able to add 2 VLAN tags to the OAM frames.
When we tried OAM with our CPE we activated the MEP on the client subif, so the OAM frames were encapsulated in both vlan (S and C) and everything worked fine : it was Telco System CPE (T280 or T380) -- Frédéric Gabut-Deloraine