Ask the Wi-Fi Guru, Episode XII

By Aaron Weiss

February 12, 2009

In the Valentine's Day edition of our monthly help and advice column, the Wi-Fi (Love) Guru shows you how to love your router--and also answers questions about daisy chaining, DD-WRT, signal boosting, and remote administration access.

February is the month you confess your love to your wireless router and beg it to explain why it won't love you back. But it will! You just need to talk to it the way that wireless routers like to be talked to. For example, chocolate and flowers are bad ideas—the chocolate will melt and short out its circuits. Flowers look nice but chances are the ones you buy aren't your router's favorite kind anyway. What a wireless router really wants is to be expertly configured. There's nothing like a nice, long configuration session to make your wireless router purr. Nowadays more and more people have two or three wireless routers, which might sound kinky but can actually be quite useful. It is, however, trickier to keep everyone happy and functional.

Q: Hello! I have a question concerning connecting multiple routers with different wireless modes. I would like to create the following:

  • Router0 acts as an AP and is connected to the Internet.

  • Router1 (Linksys WRT54G/GL/GS, DD-WRT v24 (05/24/08) std) acts as a repeater for Router0 (AP) & is connected to Router2 with WDS.

  • Router2 is connected to Router1 via WDS.

Is this possible to set up in DD-WRT v24? - Josh

A: What you describe sounds very much like a "mixed-mode daisy chain." If that sounds like a fancy technical term, it's not—I just made it up. But this is theoretically a daisy chain configuration—router0 connects to router1 connects to router2. But you're using two different kinds of relays for each link in the chain—DD-WRT repeater mode in link 1 and WDS (wireless distribution system) in link 2.

Such a setup would require that your middle router ("router1") act as both a wireless repeater client and a WDS node. I don't think this is possible. Configuring your router as a WDS node is one state of being; configuring it as a repeater client is a different state of being. As far as I know, it cannot be in both states at the same time.

The first question that comes to mind is—why mix modes? Why not configure WDS on all three routers? You can chain via WDS and maintain the same physical relationships. Your WDS configuration would look like this:

Router0: WDS with MAC address of Router1.

Router1: WDS with MAC address of Router0 and Router2.

Router2: WDS with MAC address of Router1.

Keep in mind that each wireless link halves the available bandwidth, so wireless clients connected to Router2 would max out at 25% of LAN bandwidth when exchanging data with clients connected to Router1.

If for some reason you simply had to preserve your mixed-mode arrangement, you could add a fourth router (Router1a), connected by wire to Router1. Configure Router1 as a repeater for Router0 (as it is now) and Router1a as a WDS node linked to Router2. You might do this if, for example, Router0 does not support WDS—but then, if you're buying a new router, why not simply replace Router0 with one that does support WDS?

Q: I have setup WDS with two routers using DD-WRT sp1 at my folks’ house, which is in a different town. I can remote into the base router with their IP address:port, but I want to be able to access the second router from my house, as well. Do you know how to do this or do even understand what I'm saying? - Bob

A: I do understand! In fact, I have setup the very same arrangement for remote support. But first, let's be sure everyone else understands what we're talking about, too.

Suppose you have one wireless router. Normally when you connect your browser to this router's administration interface you do so from a client inside your LAN—that is, a client connected to the router. What if you want to connect to the browser's administration page from outside your LAN—in other words, remotely? Most routers, including those running DD-WRT, offer a separate configuration setting for “remote administration" that is often disabled by default. In DD-WRT, this setting lives under Administration/Management/Remote Access. You can customize the connection port, since the usual Web port (80) is reserved for local access. From outside the network, you connect to this router using the IP address assigned to the incoming broadband connection (or use a dynamic DNS service to translate the IP to a friendly name).

Now suppose that the LAN in question is served by two wireless routers, configured to extend range through either a repeater or WDS configuration. You want to remotely admin the second router, but how do you address it from outside the LAN?

One problem is that the remote administration service listens for connections coming in via the "WAN" or Internet port. On your primary router, this is your cable or DSL modem. But your secondary router probably has no connection on the WAN port.

The workaround is that you actually access your secondary router on its "normal" administration interface, instead of using remote administration. To do this, you need to set up port mapping (aka "port forwarding") from your primary router to your secondary router.

Using DD-WRT, click on NAT/QoS and then Port Forwarding. You need to choose a public port that you'll connect to from outside the network. In my scenario, the primary router is configured to accept remote administration on port 8080. So I decided to use port 8081 for remote access to the secondary router. My DD-WRT port forwarding configuration looks like this:

Application: "remote router 2"Port from: 8081Protocol: TCPIP Address: 192.168.1.2Port to: 80Enable: Checked

The IP address is the LAN address assigned to my secondary router. Be sure to click "Apply Settings." 

Now, when I am outside the LAN and open a browser to http://myremotenetwork:8081, the primary router will forward that request to port 80 of the secondary router. Voila—I can log in to the secondary router's administration interface remotely, even though I am not technically using its "remote administration."

Q: We use an 802.11n Draft 2 network with cable backhaul for our home (and home office) network. When we upgraded our router from an 802.11g Linksys model to an 802.11n TrendNet device, we also added TrendNet 802.11n client upgrades to our computers on the network (a laptop, and a desktop that sits in a location that is hard to reach with Ethernet). Both systems received a definite and significant boost in signal strength and throughput; the connection was much faster and more dependable, particularly with the desktop because it sits the farthest from the router. About a year later, we upgraded the RAM in the old gal (it’s a five-year-old XP desktop system) and the Wi-Fi signal strength doubled. We haven’t changed anything else about location, settings, ISP, tinfoil barriers, etc. except that we put up the antenna on a radio several feet away. Are we imagining the boost? Is it a fluke, is the radio somehow assisting, or can upgrading your RAM (we nearly doubled it) actually improve your Wi-Fi reception? Thanks for your help. The Guru rules. —Naimy and Peeps

A: Fascinating! The Guru enjoys a good mystery. Honestly, I can't think of any way that the RAM upgrade would influence signal strength one way or another. It doesn't add up, and I can't find any citations online backing up such a possibility.The reason that "n" devices produce better range than pre-n devices is because the n-standard requires the use of "MIMO" technology. Basically MIMO means that multiple antennas are used. Depending on the model, all antennas may be external, or a mix of internal and external. The purpose of the antennas is to catch "multipath" reflections—basically, in the real world signals tend to bounce around rather than travel is a purely straight line. This is because they invariably hit reflective objects from glass to metal and so on.With pre-MIMO wireless, this multi-path effect resulted in reduced signal since only a portion of the original signal would reach the destination. MIMO "captures" the reflections and re-assembles the signal, thus improving performance and effective signal strength.It is actually possible that the radio antenna you mention is assisting--it could be producing a "good" signal reflection, almost like an amplifying effect. Some people have reported improved Wi-Fi signals when their cell phone is near the computer, for example, and this could be a similar kind of thing. Of course the only way to know for sure is to, you know, move the antenna and see what happens.We must also consider the possibility that the improved signal could be the result of an unknown variable--something else that did change, but you don't know it. Orientation of the PC after upgrade? Something subtle like a window screen up or down elsewhere in the room, and so on. Still, the antenna theory at least has a plausible explanation, unlike the RAM upgrade.

Aaron Weiss is a freelance writer, author, and Wi-Fi enthusiast based in upstate New York. To submit your questions to the Wi-Fi Guru, simply click on his byline (above) and put "Wi-Fi Guru" in the subject line. Click here to read last month's column. For more by Aaron Weiss, read "How to: Monitor Bandwidth with Tomato Firmware." For definitions of unfamiliar term, visit our searchable glossary.

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