Summary
How to adjust the DNS settings to ensure access to L2TP road warrior users.
Problem
I would like my L2TP roadwarriors to log on to the Windows Domain, but when my users try to log on, using the L2TP connection, they are told that the domain cannot be found. What is wrong?
Solution
The most likely cause of this issue is DNS settings on the VPN.
Check the Network > VPN > Global page and make sure that the primary DNS server is set to the IP address of the DNS server that has the Active Directory and domain information. The L2TP road warriors will need to use the Active Directory DNS server to be able to resolve the domain hostnames and services.