Connecting two internal networks

[Kadek]

Hello, I have been stuck on this simple setup for a while now. Could you tell me where is the mistake I am making?

On Ubuntu host I have created 3 virtual machines all using GRML as OS. The machine A has one internal network interface connected to network intnet1 with ip 170.30.0.1/16. The machine B has one internal network interface connected to network intnet2 with ip 10.10.10.1/8.
The third machine C has two interfaces, one for internal network intnet1 with ip 170.30.0.2/16 and a second one for internal network intnet2 with ip 10.10.10.2/8.

The problem is as follows. Machine C can ping everyone. Machine A can ping interface A1, B1, B2 and respectively machine C can ping C2, B1, B2. Altough, ip forwarding is enabled I am not able to ping C2 from A1 and A1 from C2. (1, 2 being intnet1 and intnet2)

I have checked iptables and set route tables. Tcpdump on machine B shows that either A or C do not receive arp response when trying to connect to one another.
What is wrong?

[scottgus1]

I don't think anything is wrong with the Virtualbox network setup you're using, and there's nothing you could change within the Virtualbox settings to make your network perform differently.

Internal networks only connect the guests attached to that network. If you want to interconnect two different internal networks you have to do so in the guest OS that is connected to the two networks. How to do this is within the scope of the guest OS you're running in the guest that connects the two networks, not in Virtualbox itself. The same issue would arise if you were doing this with physical PCs and physical network parts.

I would try asking the forums & support for the GRML OS you're using.

[Kadek]

Ok, thanks for clearing things up!