A response from DrayTek support;
"DHCP relay agent setup under LAN>> General setup >>Details page is implemented for local client to receive IP address over VPN.
Vigor 2925 dont support DHCP relay for remote dial-in USER.
Vigor 2960 and Vigor 3900 support this feature."

...and yet you had it working with the 3rd party DHCP Server :?: - Would that work as a 2nd Relay Agent, instead of a DHCP Server? As in, Vigor -> 3rdParty DHCP -> WS2012

Thanks for the suggestion but I am not sure that it would work. I will give it a try though. What I trying to achieve is that a Windows 10 notebook with roaming profiles and redirected files will work exactly the same over a VPN as it does over the LAN. To do that, I think, it needs to get the DHCP "Server Options" from the W2012R2 DHCP server specifically, router IP, DNS server IP's, DNS domain name, WINS server IP's and NetBIOS over TCP/IP setting. It needs to do that before the user logs in so that when they do login the roaming profile is synchronized. I thought that would be standard for a router offering dial-in VPN service to business users but do not think the 2925 is up to it. The Vigor 2960 manual suggest that it can support DHCP relay for a dial in VPN user but it is not clear that it will return all the values to the client I want. Before I buy a 2960 I will probably post in this forum and see it anyone has achieved what I want with it.

While looking for something else, I just noticed a setting that might help you...



This implies that if you use Radius for your authentication, it's not going to use the "IP Address Assignment for Dial-In Users" ... so presumably, it's going to use DHCP :?: ...

I escalated problem with DrayTek support. Problem fixed in the next firmware release according to them. They duplicated the problem of it working OK with third party DHCP but not with MS DHCP. They have sent me a Beta but have yet to install to verify. So a result. Thanks