PPTP VPN Port Routing Issues on WinXP Guest on Ubuntu Host

[indigo42]

I have set up a Windows XP guest on Virtual Box 4.04 running on an Ubuntu 11.04 host.

I need to connect to a client network with a plain old Windows PPTP VPN connection. I was able to connect after making the Guest's NIC a 'bridged' interface to the host's NIC.

The VPN connects fine, I get an IP address from DHCP, and DNS appears fine. On the WinXP guest I can use tracert and get a good 'paths' to the servers I need to connect to.

The problem is, I am not able to connect to services running on those servers. I have a WinXP laptop that does connect and I have verified that the tracert results are the same.

So....it must be something with routing ports then? I do know that Windows encapsulates TCP in something called GRE, which does not play nice with NAT, and that was the reason why I had to use a bridged connection to log in and connect.

Some other info...

The NIC on the Ubuntu host has been set to 'promiscuous mode' which I have verified by running WireShark on the XP guest with no complaints...oddly enough...the VPN 'device' does NOT show up in Wireshark, and yes...I' have WinPcap installed with WireShark.


Help?

[scp]

I am not able to connect to services running on those servers

Which services do yo mean?
I am using Windows XP and 7 VMs (also bridged networking) as Windows PPTP Client and had nothing special to config.
For example I can map Network shares and access the server with Remote Desktop.

[indigo42]

Thanks for the reply.

I'm not trying to use any "Windows" services..as in, I'm not mounting shared drives and so on.

Specifically..
I need to connect to an Oracle database..using port 1521.
I need to connect to some web apps.. http://internal.xyz.com:4489/ (and others)

All of this stuff just times out. Note that when I compare the tracert to http://internal.xyz.com:4489/ or the location of the oracle database on my Windows XP laptop, the paths are the same.

The parameters for the VPN connection is the same on both the example system (the XP Laptop) and the new XP guess

Just curious, what Adapter type did you select under the advanced section in Networking? I chose Intel PRO/100T Server (82543GC)

Thanks so much for tossing your hat into the ring! This is really confusing me! I've been using VB for years now and this is the first show-stopper I've had.

[vbox4me2]

Access servers on the other side of the vpn via their IP address instead.

[indigo42]

DNS is working. No need to do that.

[BillG]

What makes you think that it has anything to do with VirtualBox? If your vm is using bridged networking it will behave just like any other machine on the network. I would look at the firewall settings.

[indigo42]

I don't think it's the firewall because I have turned off the firewall on guest and host.

From reading, the issue seems to be something to do with briged adapters and PPTP, and Microsoft GRE. (VPN connection setting are exactly the same as my working example on an XP laptop.

I'm not blaming Virtual Box per se, but it does seem to be highlighting a problem with maybe how Linux presents eth0 to a virtualized OS?

[vbox4me2]

How sure are you things are not working as expected ? I use vpn all the time in bridge and nat, no problems. Can you ping the remote sites/servers? can you try some other service like ftp or telnet or some webserver ?

[indigo42]

As I said. I get an IP address from DHCP and DNS works, so yes, I can ping the servers.

I have several working Cisco and Juniper VPN connections via bridged and NAT on other guest working fine. Please note that Microsoft's PPTP/GRE protocol is NOT supported with NAT, you must use bridge. It's in the documentation, therefore there is something much different about PPTP/GRE than your standard VPN.

No I cannot ssh, ftp, use remote web services. All I can do is login and ping after getting an IP address.

This is a similar situation. Note it involves explicitly setting up promiscuous mode on eth0 and then adding the bridge. It's got something to do with PPTP and GRE

viewtopic.php?f=9&t=4755&p=209257#p23220

I'm on 4.0.4 so there is no /etc/vbox/interfaces and there is no VBoxAddIF command anymore. I have tried to replicate the solution in the documentation but with no success.

Also...I have Wireshark with WinPcap installed on the guest system. The VPN interface does NOT show up in the list of interfaces even after the connection has been established.

[vbox4me2]

Please note that Microsoft's PPTP/GRE protocol is NOT supported with NAT, you must use bridge. It's in the documentation, therefore there is something much different about PPTP/GRE than your standard VPN.

"A common mistake in configuring firewalls for use with PPTP is to open PPTP port 1723 (allowing connections to be established) but forget to forward GRE protocol type 47 (denying port data from passing through the tunnel)."

But also again, it is working here with GRE and NAT no firewall on the Host and both ports forwarded from the router to the Host.
A while ago I did have some sort of a problem which was solved by adding (but not using) a bridge connection next to NAT, 2 adapters.

[indigo42]

Please note that Microsoft's PPTP/GRE protocol is NOT supported with NAT, you must use bridge. It's in the documentation,
But also again, it is working here with GRE and NAT no firewall on the Host and both ports forwarded from the router to the Host.
A while ago I did have some sort of a problem which was solved by adding (but not using) a bridge connection next to NAT, 2 adapters.

Interesting...can you explain a bit more about that? I'm not quite understanding.

Thanks

[vbox4me2]

Which part, gre port or another bridge adapter?

[indigo42]

I guess the whole thing.

Is it similar to this?
viewtopic.php?f=9&t=4755&p=209257#p209257

I was trying to understand how to implement this with VB 4.0.4. There is no /etc/vbox/interfaces and such. I posted a question at the end of this asking for an update on how to do it in 4.0.4 but no one did it.

Thanks!

[indigo42]

Checking the subscribe box...been forgetting to do it....

[indigo42]

Bump