Windows Server 2008 DHCP with RRAS
- by Guillermo Prandi
I have a Windows Server 2008 R2 which is a member of a domain, but is placed in a remote location. The server is directly connected to Internet. Clients need to access a particular insecure TCP service in this server (ports 9730 and 9731). Since clients have dynamic IP addresses I cannot know in advance, I thought it would be nice to have them connected through a VPN in order to access the insecure service, but ONLY to access that service, like this:
Client ------> VPN TUNNEL ------> (Insecure service at Server)
|
\----> (Normal internet access)
I'd enable the insecure ports in the firewall only from VPN accesses.
For this I configured RRAS in the server and gave it a static IP address range (172.19.1.2 through 172.19.1.254) to serve the clients.
First I thought I could use DHCP to assign the addresses, but I cannot use DHCP in my LAN connection (not allowed by the hosting service). I tried configuring DHCP binding it to a Microsoft Loopback Adapter, but that's not supported as a DHCP source by RRAS.
What I want to accomplish is to send specific DHCP options to the client (network mask, routing table, etc.). In particular:
Prevent the client from having the server as default router (without changing the client's "use default gateway in remote network"). Have it as a route for the server's internal RRAS address only (172.19.1.1).
Prevent the client from using a 255.255.0.0 mask for the 172.19.x.x network (a 255.255.255.0 mask would be better).
Can I do that with RRAS only? How?
Currently, the only solution I can think of is to use DHCP in the LAN adapter, but filter DHCP packets so they don't reach the provider's network. However, I'm not sure if that will work.
Any suggestions are welcomed!
Guille
