I'm the volunteer support and system admin person at a small private school. We need to setup a PCI compliant Windows PC as a virtual terminal for credit card processing.

I've read questionnaire SAQ C-VT and, to quote, this computer needs to be accessed:

"via a computer that is isolated in a single location, and is not connected to other locations or systems within your environment (this can be achieved via a firewall or network segmentation to isolate the computer from other systems)"

Our setup is as follows:

DSL modem from ISP is setup to be a "transparent pipe" with no extra services. That goes into the WAN port of Linksys WRT54-GL running a DD-WRT. The LAN is 192.168.1.x. There are a couple of other WRT54-GL / DD-WRT devices. One is used as a wireless AP and another is a client bridge.

To isolate the VT (virtual terminal) machine, I have another DD-WRT device. Its WAN is connected to a port on the 192.168.1.x LAN. The virtual terminal machine is connected to its LAN which is at 192.168.10.x. The SPI Firewall etc is turned on. It's basically the default DD-WRT gateway setup where the "ISP" is our own LAN.

That's working. All incoming traffic to the VT machine is blocked, including from our own LAN. The VT can access the internet BUT, and here's the problem, it can also ping any of the computers on the 192.168.1.x LAN. I think I need to stop that.

I'm guessing that I could do something with the Static Routing table in the VT machine's DD-WRT device. I need to route anything going to 192.168.1.x other than the gateway which is 192.168.1.1 to 0.0.0.0 or something like that. That's where I'm stuck at the end of my knowledge.

Or ... do I need to get yet another DD-WRT so the network is "balanced". Maybe I need to have the internet from the DSL going into a DD-WRT which has only two devices on its LAN i.e., two other DD-WRTs, one for the main LAN and one for the VT. I think that would do but I'd like to avoid the extra cost and complexity if I don't need it.

Thanks