Wireless Network Extension with dd-wrt

RouterWith greenhouse construction moving from the structure and exterior into the interior and functionality, the need has come to extend our network range on the property. At a minimum I am going to want to run a data logger to record temperatures but the possibility also exists of automating various greenhouse systems such as ventilation or watering systems. While there are plenty of ready-made commercial systems available for this sort of thing, most of the functionality is relatively easy to duplicate and I already have a small collection of useful bits in my parts shed. Whatever form these systems take, odds are I am going to want to be able to pull data through the network to other machines for backup and analysis. I am also liable to put an old laptop I have in the garage so that I can look things up on the internet without having to go back to the house.

At the same time, my friends over at Zombie Survival Camp have just gotten the ‘net at their not-fully-off-the-grid-anymore “Ground Zero.” No doubt they will be looking to extend their wireless coverage further onto the property in the coming months and years. There are a few ways of extending wireless coverage involving better antennas and antenna positioning, boosting the power of your devices (within the limits of your local regulations if you care about such things) or simply installing various long-range devices, bridges, repeaters and so forth. I’m going to briefly outline some of what is involved in the last set of solutions — specifically how one might go about doing it on the cheap while diverting some plastic boxes and precious metals from the scrapyard. I’m not going to get into a lot of specifics since everyone’s situation will differ, but I will cover things in broad strokes.

Strategy

There are a few basic ways you can go about extending a network.

  • Ethernet Bridge – Connect two or more routers with ethernet cables. Devices can then connect to any of the routers either physically or wirelessly. Depending on the physical cable and desired speeds, ethernet can run up to several hundred meters. Wired runs are more resistant to interference and intrusion than wireless links. This setup allows for the running of several access points around the area.
  • Wireless Bridge – The exact opposite of the Ethernet bridge. Two or more routers are connected wirelessly. Commonly devices are only able to connect to the primary router wirelessly and must use cables to connect to the secondary routers. A great way of connecting a computer in a remote building but not of much use to people wanting wireless on their cell phones.
  • Wireless Repeater – Similar to the Wireless Bridge except that devices can connect to the secondary routers wirelessly as well.
  • Mesh Network – There are a few different schemes here, but the overarching principle is that all of the routers will connect to all other routers that they can access either through cables or wirelessly. Harder to set up and with the cost of some overhead processing requirements, these networks add in the benefit of redundancy and means that data can be routed in different ways if parts of the network fail.

Beyond that, there are various other networking schemes that may be of use in specific situations but the above list represents the most common and useful ways for tackling the issue of network extension for your average user.

Hardware

You can go to the store and buy devices that will do all of the above, of course, but that can cost significant amounts of money depending on your needs. Much better, I think, to use older hardware that many people have lying around or which can be acquired from charity shops or garage sales for next to nothing. This is particularly true if you don’t need blistering speeds — and if you are pulling your main internet connection in a rural area, odds are even the old equipment is still faster than your internet connection. Depending on your local networking needs, then, the old stuff is likely good enough. Personally, I have a small box of suitable routers sitting in my parts shed just waiting to be put to use. I usually pay a buck or two for them at yard sales — up to $5 for a really good one with lots of extra memory in it.

The trick here is that these devices contain chips that are actually capable of so much more than their firmware — the software built in that allows you to interface with them — will allow. Some of these limitations are in place in the interest of providing very easy access for users to the very basic functionality and to make the job of tech support much easier in walking those users through various issues they may have. Many Internet Service Providers (ISPs) will provide their own bespoke firmware to code in or automate things. Some of the other limitations are put there as a result of marketing or liability concerns, the need to meet regulations in multiple jurisdictions or other things that don’t really matter if you know what you are doing and where you are operating.

There is good news, though. Not only is it often possible to revert ISP firmware back to its factory default, many devices can actually be converted to one of the various replacement firmware packages out there. Tomato, dd-wrt and OpenWRT are all examples of commonly used, linux-based firmware packages that can be used to turn your router into a much more functional device that can then be programmed to act as bridges, repeaters or other useful devices. The ease of doing this varies dramatically depending on the specifics of the hardware and the configuration, but the good news is that for a lot of the more common devices and tasks, the process is well developed and documented. For my needs, I have always used dd-wrt and I find it provides a good balance between functionality and ease of use. I have one upcoming project where I might opt for the more versatile OpenWRT but for the purposes of extending the network to my garage, I opted for dd-wrt because I know it best.

Garage Bridge

dd-wrt router status page

The status page of my garage router’s dd-wrt install. Not a high-performance system but it will do the trick.

For my purposes I grabbed a D-Link DIR-615 vC1 from my box of old routers. It is a rather unremarkable box with a nominal 4MB of memory and non-swapable antennas. Then it was simply a matter of following the suggested procedure at the dd-wrt wiki. With this router being so common and my needing functionality provided in even basic firmware builds, there was no point to stray from the beaten path.

After it was converted to run dd-wrt, it was simply a matter of configuring the router as a client bridge, the instructions for which are also available at the dd-wrt wiki if you aren’t already familiar with network configuration. Mounted in the garage, the box now operates as a wireless bridge, linking up to my existing wireless network and connecting devices plugged into its Ethernet ports to my home network. DHCP, DNS and so forth is all still handled through my primary router, with the bridge just passing the data back and forth.

Other Configurations

I specifically chose to configure the garage router as a client bridge because I wanted to restrict its functionality to devices plugged into it with physical cables. For those looking to extend their wireless capabilities, establishing a repeater bridge is the way to go.

Those interested in a more involved project may want to consider establishing a mesh network or, with appropriate licensing, getting into HAM mesh networks or AMPRNet.

Other things you can do through re-purposing old routers include:

  • run a small server
  • if a USB port is present for an external drive, run a bigger server
  • run a pay or otherwise restricted access point
  • provide wake-on-LAN functionality to access a hibernating computer remotely
  • provide a secure tunnel from a secondary location
  • run a VPN
  • .. and a bunch of properly techy stuff

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