IPv6 VPN Provider Edge (6VPE)
6VPE is a technique that carries customers' IPv6 VPN traffic across an existing IPv4 MPLS core without upgrading the core to IPv6.
What is IPv6 VPN Provider Edge (6VPE)?
Only the provider edge routers need to support IPv6; they hold IPv6 VRFs (virtual routing tables) for each customer, and the core keeps switching on MPLS labels. It is defined in RFC 4659.