Allow anonymous access to internal, external or other network

Best Practices for allowing anonymous access to an existing Web Application or Portal.

NOTE: If you go straight and allow anonymous access on your Web Application, all users will have to click Sign In.

In spite of allow anonymous access to your web application and site collection, you should extend your web application and create a new IIS site with new hostname and then allow anonymous access

That’s is the right way because if you do all at the same web application users within intranet will not automatically authenticate in your Portal.

Trade-off: The problem is when you separate the same Site in two or more hostnames. Forms can only be submitted to one URL, so you must choice which one. That's the trade-off.
If you have a solution for that, I really appreciate your share.

Thank you.