if you have 2 networks that have the ip address scheme - 10.0.0.0/8, then you can join them via Layer3 if the addresses on both sides do not step on each other.
or in the most likely case that the addresses do step on each other, then NAT to another ip scheme is acceptable, and yes each address would have to be NATed but you can use a NAT pool for automatic NATting.
or perhaps even easier, depending on your topology, is to join them at Layer2, ie: bridge the two networks together. with a router you can use IRB. (BVI interfaces)
We are pleased to announce availability of Beta software for 16.6.3. 16.6.3 will be the second rebuild on the 16.6 release train targeted towards Catalyst 9500/9400/9300/3850/3650 switching platforms. We are looking for early feedback from custome...