Got a very strange requirement. We have a DSL router that has a firmware bug confirmed by the manufacturer where it loses it's default route outside so it can't reach anything that isnt directly connected. Directly connected for this router will be the LAN interface and the LNS that it logs onto through the WAN interface. The LNS is a 7200 series.
This router is in a data center so replacing it is a pain in the ass so I'm trying to do something clever with NAT. What I'd like to do is translate the source of my packets from the office IP to the IP address of the LNS that the router can reach. I have a "WAN" interface on the LNS that connects to the core network which is my ip nat outside interface and the virtual-template for the DSL interface is the ip nat inside interface.
How can I configure a static NAT mapping on the outside interface so it translates the source to the IP address reachable by the router?