virtualbox.org

Greetings,

vbox --> Adaptor 1 --> intnet --> guest1
vbox --> Adaptor 1 --> intnet --> guest2

According to Chapter "6.6. Internal networking" of the manual,

Once there is more than one active virtual network card with the same internal network ID, the VirtualBox support driver will automatically "wire" the cards and act as a network switch.

Neither intnet device is getting an IP address.

A few lines further in this manual chapter:
"Unless you configure the (virtual) network cards in the guest operating systems that are participating in the internal network to use static IP addresses, you may want to use the DHCP server that is built into VirtualBox to manage IP addresses for the internal network. Please see Section 8.38, “VBoxManage dhcpserver” for details."

Thank you Martin. How do I know which class the virtual network is using?

It is using nothing before you define it.
You are free to configure the network as you want.

So, you have two guests that you want them to communicate with the Internal network? Is that what you're trying to do?

From the log you attached, I see that you have an Ubuntu based OS, but you have the Ubuntu fork of VirtualBox:

VirtualBox VM 5.0.40_Ubuntu r115130 linux.amd64 (Nov  6 2017 17:41:59) release log

You can either ask in their forums for help, or completely remove/uninstall/delete/purge their version and install the official version from the Downloads section of VirtualBox (https://www.virtualbox.org/wiki/Downloads). Your VMs will be unharmed.

00:00:00.134971 [/Devices/e1000/0/LUN#0/] (level 4)
00:00:00.134972   Driver <string>  = "NAT" (cb=4)

You also have 1 network card (NIC) and that is using the "NAT" mode, not the "Internal".

Could you please describe in detail what you want to do with your VMs? The end-goal, not what you think the solution should be...

BUT... you need to install the official version of VirtualBox first, before we continue this discussion.

By assigning static IP within each vm they are now able to ping one another.

This issue is resolved.

Zentyal is an MS-SBS replacement. I am setting up a domain controller in a vm at home, and using a second vm as test client. I need to pick up another long ethernet cable so that I can vlan a port on the router. The host has 3 ethernet ports, one for the computer itself to use, another for zentyal external (bridge, vlan), and the third for zentyal internal (bridged, vlan with internal devices).

Internal means what it says. It is used internally only. There is no way you can link it to a physical NIC in the host.

You would be better off running another vm as a router between the internal domain network and your LAN. Set up a router vm with one NIC in the internal network and the other bridged to a physical NIC in the host machine.

If you bridge the vms to a physical NIC, you do not need internal at all. You seem to be confusing two different methods and using them both at once!