completely different networks
Extraordinary plain IP routing.
completely different Nats
The Bitcoin community protocol makes use of normal TCP sockets with a typical vacation spot TCP-port variety of 8333.
Using Community Deal with Translation (NAT) by many last-hop routers makes it more durable to hook up with Bitcoin nodes that use IPV4 personal addresses behind a router. In concept the usage of IPV6 addresses ought to make this concern go away.
I consider the NAT traversal for Bitcoin IPV4 TCP connections in all probability makes use of no matter options are supplied by the underlying community libraries and/or are configured within the OS by the end-user.
As far as I do know, there is not a Bitcoin-specific answer for this. There are quite a lot of common options which may be acceptable to make use of.