Cisco VRF aware NAT
http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/ipaddr_nat/configuration/xe-3s/asr1000/nat-xe-3s-asr1k-book/iadnat-addr-consv.html
https://sites.google.com/site/amitsciscozone/home/mpls/vrf-aware-nat
Nat Virtual Interfaces
VRFing 103, Using NAT Virtual Interfaces for Global Reachability
NVI between VRF’s
http://serverfault.com/questions/516979/cisco-1921-using-nat-nvi-method-between-vrfs-slow-
performance
Old VRF aware NAT config
https://sites.google.com/site/amitsciscozone/home/mpls/vrf-aware-nat