VPN issues in Windows 2008

I have a VPS w/ 1and1 (I know I know...) and I'm trying to setup a VPN. Here's the setup:

I only have one NIC on this VPS so I setup the server using this guide: http://www.thomasmaurer.ch/2010/10/how-to-install-vpn-on-windows-server-2008-r2/ - The IP address pool is 10.0.2.1 to 10.0.2.20 and the server is nabbing 10.0.2.1 for it's self

Now the VPN is working fine and the users are authenticating okay. The problem is I can only ping the server from the clients *sometimes* but the clients cannot ping one another at all. I say sometimes because for a large majority of the time after the setup it would never ping the server but today it finally was able to ping it. Thing is, nothing changed.

The reason I want to do this is so I can lock down the server where the only thing that is able to be pulled publicly is the HTTP, FTP, Plesk, Mail and VPN server while the rest is blocked including RDP and be able to get into the VPN and access the rest. I think I have the Windows Firewall stuff figured out but the VPN the biggest thing right now.

Any ideas?

Also, when I initially connected to the VPN I couldn't browse anymore but read about the "Use default gateway on remote network" trick and can browse just fine now. The VPN client is getting a good IP but the default gateway is blank if that helps any. Below is IPCONFIG.

PPP adapter VPN Connection:

Connection-specific DNS Suffix . :
Description . . . . . . . . . . . : VPN Connection
Physical Address. . . . . . . . . :
DHCP Enabled. . . . . . . . . . . : No
Autoconfiguration Enabled . . . . : Yes
IPv4 Address. . . . . . . . . . . : 10.0.2.3(Preferred)
Subnet Mask . . . . . . . . . . . : 255.255.255.255
Default Gateway . . . . . . . . . :
DNS Servers . . . . . . . . . . . : **Censored, server IP**
195.20.224.234
NetBIOS over Tcpip. . . . . . . . : Enabled

 

Strange... I reconnected all of the VPN clients at the same time now they are communicating, albeit a horrendously high ping but at least it's working. Any ideas why this is happening?

[EDIT] High ping is because of the wifey watching Netflix. Ignore that part. Basically it's an intermittent connection at this point.

 

Just wanted to throw up an update to the thread.

I read online that changing the MTU from 1400 to 1472 would fix the problem. When I did that, it totally killed off the VPN server. It wouldn't even start anymore.

I got 1472 by starting from a ping with a 1492 and working my way down until the ping actually went out and that was the highest number that had a successful ping.

HELP!