Ask the Wi-Fi Guru About Wi-Fi for a Remote House

By Aaron Weiss

April 11, 2011

Our monthly Q&A series offers advice to those seeking help with home or small business WLANs. This month our guru helps a reader straighten out virtual SSIDs and considers one of the more complicated Wi-Fi repeater situations he's ever addressed on our pages.

Our monthly Q&A series offers advice to those seeking help with home or small business WLANs. This month our guru helps a reader straighten out virtual SSIDs and considers one of the more complicated Wi-Fi repeater situations he's ever addressed on our pages.

Would you like to ask the guru a question? Write the editor.


Have you ever tried to debug a tech problem for a friend or family member by talking it through over the phone? Even for the experienced tech savvy person, the experience can be an exercise in frustration. "Try clicking cancel. What does it say now?" "Which window did you close? Are you looking at the browser now? Or the control panel?" With each question, and each ambiguous answer, you edge ever closer to an open window, hoping that maybe you'll fall out before the ordeal is over.

Sometimes the person you are helping lacks the experience to provide you with useful narration. But sometimes the problem isn't them at all, but the design of the product or software you're trying to wrangle. Take the case of a Netgear wireless router, recently installed by a family member. He'd proudly setup the router himself, plugged in the cables, walked through the setup wizard, and yet the laptop did not see any available wireless network.

We walked through all the usual scenarios. Could the laptop be at fault? (No, it did see neighbors' networks.) Could there be an issue with the wireless-n router talking to a wireless-g laptop? Could there be an issue with security? Exploring each step by phone ate up lots of minutes and got us nowhere. In a desperate measure, I suggested we poke around the "advanced" menu of the wireless router's administration interface. There, like a glowing beacon, hid a most promising setting: "Enable wireless radio". And it was…unchecked.

Guess what? Your wireless router needs to be enabled to actually work. Who would've guessed? My question is, why was it disabled in the first place, fresh out of the box? Why would a manufacturer of a wireless router consider enabling the wireless radio a special, advanced situation?

Using DD-WRT, which SSID do I want to connect to?

Q:When I want to connect to a wireless network using a repeater, I see two networks, the "physical" SSID, and the Virtual SSID from the repeater. On which one do I have to connect? - Stefan

A: When you follow the linked tutorial using DD-WRT to configure a wireless router as a repeater, the router needs to behave in two different modes at once. Normally, a wireless router behaves in broadcast mode, sending out wireless data to associated clients. In special configurations, a wireless router can behave in client mode, where it instead receives wireless data from another router. You can use this configuration to build a bridge, connecting physical devices to a wireless network even though they may not have a wireless adapter built-in.

In repeater mode, a wireless router needs to play both sides of the fence. Because the typical wireless router only has one radio, it can only behave in one mode or the other but not both at the same time. To get around this limitation, firmware like DD-WRT that supports repeater mode causes the router to alternate between modes, rapidly switching between receiving and broadcasting data. In setting up such a situation, you configure a "virtual SSID" which represents the network name of the broadcast mode. So when connecting to a repeater, it is the virtual SSID you want to use.

Note that when you setup a repeater, the throughput (network speed) available to associated clients is halved compared to clients using the primary router. This is because, by virtue of playing the roles of both client and broadcaster, the repeater router's radio can only be used for each role half the time. For more on this situation, read on.

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