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I have a VM that I would like to do some network experimentation on. Currently it is running Xubuntu 12.04 on VirtualBox but I'd be willing to change that up.

I would like to have 2 network interfaces set up - one that has access to my internal network, and one that has access to external traffic.

The end goal of this would be so that I can throttle external traffic without throttling internal traffic as well.

I used to run a firewall server that functioned like this (Smoothwall) but since this is a device on an internal network I can't wrap my head around how to configure it.

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You just do it. The manual tells you the meaning of the various adapter modes.

You'll want one that's NAT (Network Address Translation) for sharing your host computer's Internet connection. Then you'll want one that's either a Host-only Network or an Internal network (depending on whether you want to communicate with other VMs on the same system). Just go into your VM's Settings and Add a new Network adapter with the appropriate type(s).

Once you add the hardware to the guest, you'll see the adapter come up when you boot the VM, and it'll have its own private IP space (at least in the case of the internal/host-only network). This is isolated from the public internet. But since the guest is multi-homed (it belongs to both your NAT to the public internet and to the private LAN), a compromised process running in the guest will be able to access the public Internet unless very strict per-process privileges/ACLs are defined to prevent processes from accessing the Internet NIC or routing through its network. But since I have no idea what you're actually trying to do with this VM, I can't say whether you should worry about this or not.

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"Internal Networking is similar to bridged networking in that the VM can directly communicate with the outside world. However, the "outside world" is limited to other VMs on the same host which connect to the same internal network." This doesn't do what I want. I need one adapter to speak to the outside world (through my modem) and one to speak only to my internal 192.168.*.* subnet. Is that even possible? – javanix Jul 23 '12 at 18:07

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