I have a MPLS network that I want to hide. My idea would be to have the Adtran create a L2TP tunnel back to a Cisco ASR903 that makes my site router appear as if it is layer 2 attached to a Host router. I do not want the Site Router to participate in any routing protocols in the MPLS cloud. I typically deploy VPLS for Layer 2 connectivity but in this instance my WAN connections are nxDS1's, which I am told does not support VPLS. I tried to use GRE tunnels between the Adtran and the ASR903 but that still requires me to route between the Adtran and my site router, which exposes the Adtran that I want to make transparent.
L2TP is not currently supported on our AOS NetVanta products.