Last Updated on August 6, 2018 by Dave Farquhar
Most of us have an old router like a Linksys WRT54G laying around, or if we don’t, it’s very easy to find one–the nearest garage sale or thrift store is a good bet–but sometimes all we need is a switch, to hook up a couple more computers or other devices to a wired connection. Using a router as a switch wastes some of its capabilities, but it’s easy to do. Here’s how to use a router as a switch.
How to use a router as a switch
The first step is to disable the router functionality you aren’t going to use anymore, so it doesn’t interfere with the functionality on the router you still use as a router.
Connect your old router to a computer without connecting it to the Internet. Find your IP address (the command ipconfig /all will usually do) to ensure you’re able to communicate with the router. The router probably lives at 192.168.0.1 or 192.168.1.1. Connect to that IP address with your web browser and see if that pulls up the admin page.
Disable DHCP
The first step after you connect to the router’s admin page and disable the DHCP server on the router. If you have more than one DHCP server on your network, your network is going to be a mess. Thanks to Dave (not me), a longtime reader, for bringing that up.
Assign your router an IP address that won’t conflict
You also want to make sure your router’s IP address doesn’t conflict with any others on your network. Set its IP to 192.168.1.2 or something else not in use on your regular network. Then write the IP address down and tape it onto the router, in case you ever need to connect to it again and configure it.
Re-assign your WAN port if you can
If you happen to have DD-WRT loaded on your old router, you may be able to assign your WAN port to the switch. This will give you an extra port. This functionality usually doesn’t exist on stock firmware, and I can’t guarantee every DD-WRT build on every router has this option. But having five ports to work with instead of four is always nice.
Disable wireless
You will also probably want to disable wireless as well. You don’t want the router sending out wireless signal that doesn’t connect to anything, as this will just frustrate people, and likely also interfere with the wireless signal you’re actually still using.
Now that you’ve made the necessary changes, save your changes. The router may want to reboot. That’s OK. Let it reboot, unplug your computer from your old router, and then wait for its status lights to come back on.
Connecting up your router as a switch
Once you have DHCP and wireless disabled and you’ve eliminated the possibility of an IP conflict, all you do is ignore the router’s uplink port. Just plug the router into your other one with a regular switch port. Depending on your routers, you may have to use a crossover cable instead of a standard Ethernet cable, but by all means try a plain old Ethernet cable first. Then plug a computer into one of the other switch ports and make sure you can access the rest of your network and the Internet.
If you do that, your spare router will function happily as a dumb old switch. It’s even possible that a broken router that no longer functions properly as a router will still function as a switch, so it’s worth trying. That’s happened to me. I’ve had routers sustain damage after power outages but still function as switches.
And that’s how to use a router as a switch. There are some caveats to this, but it’ll work.
Energy usage
If you’re going to leave things hooked up long-term, in the long run, you’re probably better off getting a cheap gigabit switch because it will give you better performance and use less electricity. I cut my energy usage 19% in 2011, which worked out to about $171. That’s a lot of money, so I don’t recommend nickel and dime-ing in the other direction. But if you need a switch in a pinch for a temporary setup, an old router can work just fine.
Other potential uses for an old router
There are lots of uses for your old router, including creating a DMZ or a guest network. Running DD-WRT tends to increase its capabilities, so here’s how to check if it works with DD-WRT. But a switch in a pinch works too.
David Farquhar is a computer security professional, entrepreneur, and author. He started his career as a part-time computer technician in 1994, worked his way up to system administrator by 1997, and has specialized in vulnerability management since 2013. He invests in real estate on the side and his hobbies include O gauge trains, baseball cards, and retro computers and video games. A University of Missouri graduate, he holds CISSP and Security+ certifications. He lives in St. Louis with his family.
Best be sure it does not have DHCP running or you may have issues.
Oh, by all means yes. Thanks for bringing that up; I generally have DHCP disabled on my routers anyway so I haven’t run into that. I’ll update the post with that advice.