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For some reason, I always used to think that setting up two routers on the same network would be hard to do. Turns out that it is surprisingly easy, but it’s just not widely understood. Granted, people rarely have to do this, but it’s pretty useful if you do. So I figured I’d document here the relatively small number of steps needed to get this working.

For those of you who are saying, “why would you ever need to do this?” let me explain. My house came pre-wired with ethernet, which was awesome. Each room has an ethernet jack that all feed to a central location. Unfortunately, that central location is in my bedroom closet downstairs. Now, I get cable from a DSL modem which is upstairs in the family room. I used to connect the DSL modem via the one ethernet port to a router downstairs in my closet. But I recently got an Apple TV that needs to be upstairs in the family room next to the TV. So I needed to be able to connect both the AppleTV and the DSL modem to the rest of the network, but I only had one ethernet port. Therefore I needed a second router to sit upstairs between the two upstairs devices and the ethernet port. But without changing anything, that two router configuration meant I had two networks and computers on one couldn’t easily see those on the other.

In the past, I just suffered with two separate networks, one for the upstairs devices and another for the downstairs machines. But finally I thought to myself, there has to be a way to do this. A little research, I was able to setup a network that spanned two routers fairly easily. Now machines upstairs can easily connect to the downstairs devices. W00t!

Here’s how to setup a network with 2 or more routers. We’ll assume Router A is the primary router connected to the DSL or cable model and Router B is the secondary router. We’ll also assume that Router A is already configured properly to connect to the internet via the DSL or cable modem.

Connecting two routers to form one single network:

1. Get both routers in close physical proximity to one another and to at least one computer
2. Connect an ethernet cable between one of Router B’s LAN ports and the computer.
3. Log in to the Router B’s web interface and disable DHCP on that router (consult your router’s manual or manufacturer’s website for more information on this)
4. Change the LAN IP address of Router B to something other than the default (e.g.,192.168.0.2)
5. Run a normal ethernet cord between one of the LAN ports on Router A and one of the LAN ports on Router B. Do NOT connect the cable to the WAN port on Router B (this is a common mistake)
6. Disconnect the computer from Router B and reboot Router B just to make sure it acquires a new IP from Router A
7. Connect an ethernet cable between one of Router A’s LAN ports and the computer and check what IP you get - it should be something like 192.168.0.3
8. Disconnect the computer from Router A and connect it to one of the other LAN ports on Router B
9. Check what IP you get now - it should be in the same IP range as before, something like 192.168.0.x
10. Plug Router A into the DSL or cable modem and wait until the lights indicate that it has acquired an IP
11. Using the computer still connected to Router B, verify you can reach the internet

You’re DONE! See, pretty easy, right?

My apologies to my last roommate Phil who used to struggle with the old network topology of our home. But if anything, hopefully this post will spare other roommates a similar struggle.

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