I have setup my SharePoint 2013 server with external access via AAM using the external FQDN as the default and the internal one as 'Intranet'
I can access the site externally using anonymous access but 2 problems:- A. no content shows on the page and B. when I click 'sign in' internally it just loops the page, not actually signing me in, but externally, it just redirects to the internal FQDN but without prompting for credentials.