So, whilst possible to do, and this blog is a brilliant guide to doing it, but there are better ways. if this is a network you own either end, then if you real

So, whilst possible to do, and this blog is a brilliant guide to doing it, but there are better ways. if this is a network you own either end, then if you really do have the same subnets issued to different sites, then you would be better served having virtual interfaces/VLANs to have a second IP address. Or, just use ipv6, and you have enough IPs to do what you want. You can use 6to4 or nat64 to get IPv4 connectivity. most modern networks terminated services on the edge with loadbalancers, so you can use them as 6->4 bridges.