Sophos UTM L2TP over IPSec setup question

I am using 9.719-3. 

I found this documentation:
docs.sophos.com/.../Remote_Access_Via_L2TP.pdf

The problem is we are using RADIUS and when the user connect to the VPN DNS does not work. I have even added the DNS servers to the Remote Access -> Advanced. I wonder looking over the method for not using RADIUS if there are some firewall rules that are missing possibly to allow DNS to work for the VPN users? Since we are using RADIUS there is no "users and groups" option. 

Thanks,