IP Addressing

As long as there is no connection between the two, none.

If Internet connection is required then use one of the reserved address ranges and make sure the router between you and the Internet does not route that range (most don't by default).

enjoy

If there is no connection between your network and the Internet and never will be, there's no problem. Even if there will be a connection, if you use a NAT router between you and the Internet, there's still not a problem.

The main implication isthat it's a whole lot easier to adopt an IP addressing scheme early and stick to it than it is to change later on.

The main concern is that if inadvertent or unplanned connections occur between your network and the Internet, it could cause routing problems for the folks who own the IP addresses you're using.

paul