Hello,
I’m using Mikrotik as VPN concentrator for Windows clients. I’m using external Windows DHCP server to push additional parameters (routes, domain suffix) to native Windows VPN clients (PPTP / L2TP / SSTP).
I tried to use DHCP server on Mikrotik, but Windows VPN clients doesn’t accept DHCP responses (DHCPACK). I caught DHCP responses from Windows and Mikrotik DHCP servers and compare them. Only difference that I found is in HTYPE; VPN client sends DHCPINFO with HTYPE=Hyperchannel (8), response (DHCPACK) from Windows server has HTYPE=Hyperchannel too, but response from Mikrotik server has HTYPE=Ethernet (1). I think this is the reason why Windows native VPN client doesn’t accept response from Mikrotik DHCP server. I can’t test it, I don’t know how I can modify packet (HTYPE) in response from DHCP server.
I made simple UDP responser, which fixed original Mtik response packet. The problem is definitively in HTYPE and HLEN. When I fixed HTYPE to 0x08 and HLEN to 0x00, Windows VPN client accepted this response. I already opened support ticket.