How to Set Up Public WiFi at a Small Business

This is a quick writeup of how I set up public wifi access at a small business. The method employs two routers sharing one cable modem connection. This allows a point of sale (POS) system and the public wifi to be on separate networks. This prevents anyone from trying to sniff out credit card transactions. It also uses some basic quality of service (QOS) settings to prevent people from hogging bandwidth from the POS system. Here’s what you will need to duplicate my setup.

• A wireless router than can have the Tomato Firmware installed on it. I recommend the Linksys WRT54GL
• A wired router with a DMZ port
• The Tomato Firmware

Now for the setup.

1. Download and install the Tomato firmware onto the wireless router. Tomato makes a wireless router much more stable and adds features that you’ll never have with the stock Linksys firmware such as real time bandwidth monitoring, QOS settings, and much more. Carefully read and follow the instructions included in the download. If you do not know what you are doing you can brick your router so don’t skip reading the installation guide.
2. Attach the cable modem to the WAN port of the wired router with a patch cable.
3. Enable DMZ on the wired router and connect the DMZ port of the wired router to the WAN port of the wireless router with a regular network cable.
4. Attach the POS system to an available LAN port on the wired router.
5. Set the routers to be on different subnets. For example, set the IP of the wired router to be 192.168.1.1 and the IP of the wireless router to be 192.168.2.1. This will prevent DHCP conflicts.
6. Change the default admin passwords for both routers to something else.

At this point the setup should be working and all connected computers, wired and wireless, should have internet access. All that’s left is to enable some QOS setting to ensure the POS system will always have bandwidth. This step is optional but could save a headache later on in the event someone decides to abuse the wireless network.

1. Run an internet connection speed test and note the maximum upload and download bandwidth.
2. Enable QOS in the Tomato settings on the wireless router.
3. Under the QOS “Basic Settings” page set the inbound and outbound limits to be a little less than the values from the speed test. In my case I left a quarter of the upload and download bandwidth for the POS system just to be on the safe side.
4. Save your settings. Confirm the settings work by running separate speed tests for each router. The speed for the wireless router should go only to what you set the limit to be.

That’s it! The total cost of this setup is easily less than $100 and in my experience has been very reliable.