DNS not working with VPN

Question

I've done my best to search for an existing discussion on this topic, but couldn't find anything conclusive or exactly the same.
I'm brand new to Apple and OS X Server, but think I have made good progress with this one exception.
Setup: XServe with OS X Server SL setup as a Gateway directly behind an ISP/Cable modem. WAN configured and connected to the ISP, and one LAN with the default setup at 192.168.1.x (DNS at 192.168.1.1). I used the Gateway Assistant to get basic network settings initially configured, including DHCP, Firewall, DNS, and VPN.
I'm using DNS with a single primary zone for internal domain purposes and forwarders for Internet resolution. I have customized it to include various machine records within my LAN. Outside of the LAN, DNS is handled at register.com to point all traffic to my servers WAN IP.
In short, when connected directly to the LAN, all works like a charm. Internal DNS handles everything perfectly, and connects to the Internet for everything else.
However, when I connect to my environment from the Internet via VPN (LT2P and PPTP) and a Mac OS X SL client machine DNS doesn't seem to function and I can't even ping my DNS server by IP (192.168.1.1). Any attempt to ping any resource by name including my primary zone's FQDN fail/timeout. I can only ping other LAN resources by IP.
Not sure if this is useful or a valid test, but when I establish a VPN connection while on the LAN, everything works great and as expected, and I seem to get the exact same network settings assigned by the server as when coming from the Internet.
Just not sure where to go from here? I seem to be on the LAN via the VPN, just can't really use it effectively if I can't leverage internal DNS.
Any suggestions would be much appreciated.

Answer 1

Have you manually entered your server DNS in the VPN DNS settings tab of your client machine? This may not be applicable to you as we use a hardware VPN router as we never could get the Mac VPN working. However, if i connect to our VPN without the DNS entered in my PPTP config I experience a similar issue as you. I can access our shared AFP, ping IPs, but not resolve domains. To fix this I put both our primary and secondary internal DNS plus search domain in the System Preferences/Network/VPN(PPTP)/Advanced/DNS tab of my PPTP connection.
Also i noted that if you have multiple configurations under one VPN interface - all configurations will be set to that DNS. To get around this i had to add multiple VPN interfaces for my various VPNs instead of using multiple configurations under one interface.
Not sure if this will help but its what worked for me. I am new Server as well and been trial and error setting up a couple Mini Servs. It look me a while to break enough things to figure it all out but I now have a slick little setup.