My take -
Irfan Shakeel over on the Alienvault blog shows step by step how to fire up a kali image in aws under the free tier. This is faster than fiddling with your router settings, and safer too.
“Configuring Kali Linux on Amazon AWS Cloud for free
…The best possible way to accomplish your objective is to host Kali Linux in the cloud, where the vendor manages the network and server, so you can focus on your pentesting. Plus it’s FREE!… In this article, we will talk about the steps to configure Kali Linux on Amazon AWS cloud for free.”