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Ask Slashdot: Best Way To Solve a Unique Networking Issue?
New submitter petro-tech writes: I work as a service technician, maintaining and repairing gas pumps and POS equipment. In my day to day activities, one that consumes a ton of time and is relatively regular is the process of upgrading the software on pumps. This is done by connecting to the pump via direct ethernet from my laptop, then running a manufacturer-provided program that connects to the device and pushes the new software. Some sites have 8+ pumps with 2 devices in each, and at 20-30 minutes apiece this can be quite time consuming. Unfortunately the devices are not actually on a network, and as such cannot be updated remotely, also since they are not on a network, they are all configured with the same IP address. Additionally the software doesn't allow you to specify the adapter to use. I would like to be able to get to a site, connect a cable to each pump, and load them all at the same time. The only way I can figure to accomplish this with the software we've been provided is to do this: Get a 16-port powered USB hub, with a usb-ethernet adaptor in each port; Set up 16 VM's with extremely stripped down XP running on each, with only one USB-ethernet adaptor assigned to each VM; Set XP to boot the application for loading software as its shell; and load each device that way at the same time. Is there a better way to accomplish this?
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I think what he's asking is whether or not he can network them together even though they all have the same IP address. And the answer is yes.
As a network engineer, I can think of a way with a Cisco catalyst switch, OR, a linux box with multiple ethernet ports:
For a Cisco switch, get a layer 3 switch, enable ip routing, put each switch port on a separate vlan, create an SVI for each vlan that is on a /30 subnet using the first address of that subnet. Create an access control list so that all traffic that goes ingress to the second IP address of the vlan subnet has its destination address changed to the static IP address of the equipment and the source address changed to be the IP address of the SVI, and then change all egress traffic from the second subnet IP to change the destination address to match that of your laptop and the source address to match that of the second IP address in the subnet.
For a linux box you'd do the same thing, only using SNAT and DNAT in iptables.
Effectively what you're doing is creating a NAT table that allows you to uniquely address each device, without actually changing the IP addresses themselves to become unique.
If you're not very affluent in networking, the above will sound VERY confusing, but trust me it can be done.
Crappy used laptops are cheap. You don't need 16. You need 4. The first one will be about done by the time you get the 4th one started.