Private Company Network

I’ve got some questions regarding coonecting 2 ethereum nodes (geth) between two different networks: e.g. company A and company B.

First, I’ve already connected two different nodes within the same network (via enode info, adding the enode info to a static nodes json file together with each IP address, etc…).

Is there any guideline for the steps neccessary to connect two nodes which are in different networks?

Can anybody tell me in detail what steps are neccessary to go through when thinking about networking these different nodes?

Are there any aspects which are crucial for a secure private network?

Further questions:

What happens when a node has a dynamic IP?

Do I have to define bootstrap nodes within this company network?

What about firewall settings?

Are there any other interesting aspects I missed out so far?

Maybe someone already went through all these steps and could help me out here. Would be awesome to find some people to work through all these problems!

Thanks