APM Captcha and Active Directory with Route Domains an 10.2.4

I'm trying to implement the Google Captcha solution below an APM Logon mask as described in this article. I found out that DNS is not working outside the Common Route Domain 0, so we need to replace www.google.com with one of its IP-addresses. So how do I need to specify this in the HTTP AAA configuration?

Thank you!

Ciao Stefan :)