MPLS over IPv6 GRE encapsulation and de-encapsulation

This feature enables MPLS traffic to be transported over IPv6 GRE tunnels using a flexible tunnel interface (FTI), with support for both encapsulation and de-encapsulation. For encapsulation, MPLS packets are carried as the payload of GRE packets with an outer IPv6 header for transport across an IPv6 network. At the receiving device, the outer IPv6 and GRE headers are removed so that the original MPLS traffic can continue through the forwarding path.