can a router plug plug into Port #2 into on a 2 port ION?

What are you attempting to accomplish with this setup? What is your intention with the two network ports? What you're attempting to accomplish will in large part determine the answer. Although generally speaking each physical port on the console should be on its own separate network (ie, a lighting network versus a data network, or perhaps a wireless network to permit for focus apps, etc. Once configured a sepectic way, you generally should not be adding unnecessary complication by swapping how the ports are used. 

If on the other hand you have a simple single network, then your router would be connected to port one, and all other devices should be connected to the router, not passing through the console.

What are you attempting to accomplish with this setup? What is your intention with the two network ports? What you're attempting to accomplish will in large part determine the answer. Although generally speaking each physical port on the console should be on its own separate network (ie, a lighting network versus a data network, or perhaps a wireless network to permit for focus apps, etc. Once configured a sepectic way, you generally should not be adding unnecessary complication by swapping how the ports are used. 

If on the other hand you have a simple single network, then your router would be connected to port one, and all other devices should be connected to the router, not passing through the console.