I don't have public ip address and no access to router settings in my workplace. But I often need to expose my local web server to clients or coworkers so that I can quickly show them some progress, new feature, missing thing or whatever.
I found that the easiest way to do that is to use a little gem called Localtunnel.
When you have Localtunnel installed on your machine it's just a matter of issuing this command from your terminal:
Where 8000 is the local port you want to expose. As the output of the command you receive a url which you can share with your clients and which points to your local web server.
Please look at Localtunnel homepage to learn how to install the tool.