A friend and I were experimenting with new network configurations for his Wireless ISP. He runs a lot of services and has a very extensive network and is growing, fast.

Recently he installed an Untangle server so that his users would get less Spam, he could start shaping traffic/dealing better with PeerToPeer traffic and other such things. He really likes the product and when it came time to add a few servers to his network we decided to virtualize them in VMWare.

The preferred configuration for this system was
VM1 : Untangle
VM2 : Web
VM3 : Mail

All well and good until you understand that Untangle is a Transparent Bridge, it needs to sit on the network between machines so it can manage all the traffic. Transparent Bridges are a nice piece of Layer 2 magic that look like a Firewall but are zero config and do not require network changes, NATs etc. They simply grab all incoming traffic on the external port, sorts and manages packets and then passes approved traffic/modified traffic onto the internal network. Likewise for outgoing traffic (swap external/internal). All “Internal” machines get External IP’s so you get the power of a traffic shaping firewall with the simplicity of a single network.

So, how does this work on a VMWare box? Easy and obvious but I want to confirm it works and works well.

Obtain a server with more then one network port. VMware Server will route packets between them even if they are not physically connected. So, in this example we put Untangles external network on ETH0 which was “connected” (configured really, its a VM) to speak to the outside network and then we configure its internal network to bridge to ETH1 which has no network connected.

Any protected VM’s just get configured to use the Physical ETH1 as their device. Give them an external IP address (its a transparent bridge, remember, not a firewall) and you will be off to the races.

Bonus, you can connect a physical network segment to ETH1 and Untangle in the VM will protect both the Physical and Virtual machines.

Its quite slick and I am very impressed, good work Untangle.