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We are using VirtualBox 3.0.4 in a networking course to simulate a network.
We have an XP client with a PCnet-FAST III network interface and a Windows Server 2008 with an Intel PRO/1000 MT network interface.
For both of the guests we use two network adapters :
- an internal network (same network name has been checked)
- a NAT adapter for external connection within our guest OS.
Last Saturday, for two of the eight course members, this configuration did not work. Client could not 'see' the server.
Both the server and the client have fixed IP's as follows :
XP client : IP 192.168.2.150 - Mask 255.255.255.0 - GW 192.168.2.100 / Server 2008 : IP 192.168.2.100 - Mask 255.255.255.0 - GW 192.168.2.100
Ping from client to server and from server to client on IP-address was not successful. We disabled the firewall both on server and client, no success. We double-checked all settings, we disabled the NAT interfaces, but nothing worked.

What might be the problem ? Could anyone give me some useful tips to solve this issue.

Thanks !!

Internal network will allow the guest to see each other but not the host or Internet.
Adding NAT will give the guests access to the Internet, but will not allow them to see each other without port forwarding.
Since I do not know where the server is in this scenario I can not tell you why it is not being seen, but there also may be a limit to the number of Internal guests that are allowed.
As a suggestion I would get a $40 router and used Bridged mode.

Thanks for the reply.
I have been using bridged networking in the past, but since the computers using the virtual environment are connected with the school network, I experienced that there was interference of the school server when the virtual client tried to connect to the domain of the virtual server. The school server acted in this as a gateway (router).

This is why I use the mentioned configuration. I did not have any problem with this until last Saturday.

What if you don't set a gateway for the internal network? Did you also try it without the NAT adapter? You can easily disable the adapter on the Guest OS itself, or unplug the virtual cable through the VM settings, or when it's running through the network menu icon (right click the icon in the status bar).

As I mentioned in my first post, I disabled NAT on both server and client.

The gateway has been cleared on the server, but I did not disabled this on the client. This might be a solution, I will try it next Thursday (next course day).

Still strange that this issue occured on two of the eight computers in the class. On the six computers where it worked without problem, we did not disable the gateway neither.

Thanks anyway for the suggestion. I will post the result as soon as I know more.

Hi Sasquatch,

Your suggestion about leaving out the gateway on both client and server did not work. I tried a few other things, but nothing worked.

I finally used bridged networking. Now the students can login from XP Client to Windows Server 2008.

Thanks to those who replied !!