Hi every one, I would like to change our L2TP VPN from locally authenticated users to Active Directory-user. (We don't use of Radius server.) Is there any way to do this?
You would need to setup a RADIUS server to authenticate against AD Users. On modern versions of Windows server, it's part of the Network Policy and Access Services role.
Search in the KnowledgeBase on l2tp radius. The first article listed is the guide to doing what you want. Also search on wireless radius - although the UTM section doesn't apply to L2TP/IPsec, the Windows portion is documented with screencaps that make it more understandable.