Excalibur's Sheath

Creating Two Networks Which Share an Internet Connection

Sep 11, 2016 • linux,networking

Recently, I decided to create a second network in my home for testing computer systems. I wanted to keep these systems from being able to access my main network. After doing some research I decided to make use of another router, and a different subnet mask to accomplish this. My previous setup already has a second router plugged into our Google Fiber box. Many people find the Fiber box to be extremely limiting, and our Fiber box also has a wifi radio, which does not quite reach to the back of our apartment. I added a Linksys 1200AC router to help overcome this. Off of this router I have been running a network on the 10.18.57 with a subnet mask of I have its DNS servers pointed to the OpenDNS server IPs.

I have all of the phones, tablets, and our main computer on this network.

Recently, I wanted to make a second network for my own use. I also did not want to buy any new hardware for this project. I wanted some of my devices open to the internet. I happen to have a couple of old Linksys WRT54G routers. One of them has ddwrt, while the other has Tomato firmware. I had wanted to use the ddwrt router, but it did not work this time, so I ended up using the Tomato Firmware router.

The steps were:

  • Plug a network cable into the Google Fiber Box, and the new router
  • Plug a cable into the router and a computer to access its admin panel
  • Setup the new network on the router

I have DHCP turned on on the Google Fiber box. It currently has two devices attached to it. They receive their IP Addresses via DHCP, with static leases. I setup the WRT54G router to use a network of 10.18.55, and a subnet mask of I noticed that it made both a LAN with the settings I setup, and a bridged network. I also have the Tomato router using DHCP to give out IP Addresses.

I opened the ports I was interested on the Google Fiber box, and on the Tomato router.

When I checked the devices on the new network were able to reach the internet, and I could SSH into the computer from the internet, but devices could not talk across the local networks, which is what I wanted.

What my network looks like now is this:

      |Google Fiber Box|
              / \
             /   \
     --------     -------- 
     |1200AC|     |Tomato|
     --------     --------
        |             |
     --------     --------
     |Secure|     |Test  |
     --------     --------

The two networks are running really well.