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Friday, December 7, 2012

WiFi -Universal repeater
I have an tp-link wa801nd repeater/router and an AVM FritzFon box connected to our DSL line.  
What does work:
WEP (not WPA) and set the repeater to be a "universal repeater", not just a "repeater".
What did not work:
WPA + set the repeater to be a "repeater" and tell the Fritzbox to allow WDS (wireless distribution). My impression was that the repeater would associate for a little while, then unbind, confuse the clients and a few minutes later bind again.
What would have been OK:
Tell the tp-link to act as an access point and bridge. Let it have its own SSID and run its own DHCP. Clients could associate to this and the tp-link should pass their packets to the Fritz box.
Clients could associate, but their packets did not seem to be gatewayed to the fritz box. I did try setting the gateway on the tp-link to its IP address and to that of the fritz box.
Despite visiting 100 websites, I cannot see the difference between "repeater" and "universal repeater" or at least I cannot find why one would use "repeater".
A lot of this is poorly documented by the manufacturers. They’re not even consistent in the use of the terminology, and often leave out meaningful details. Perhaps it’s so complicated they just fear that providing this information would only confuse ppl further.
The difference between Repeater and Universal Repeater is that the former requires WDS (a bridging protocol developed years ago), whereas the latter does not.
The problem w/ WDS is that it’s NOT a wifi certified protocol, so implementations vary across manufacturers. And that means incompatibilities abound. When you use a Universal Repeater, it uses wifi certfied protocols (B/G/N), so it will connect to virtually anything else supporting these same protocols, regardless of manufacturer (that’s why we call them standards!).
Unfortunately most manufacturers don’t get into all the minutia. Instead, they take a short cut and basically tell you to try Repeater (WDS) first, and if that doesn’t work, switch to Universal Repeater. What they’re assuming (hoping) by this strategy is that you’re using ONLY their own wireless devices, and therefore there won’t be any compatibility issues wrt WDS. But should that not be the case, should you be using DIFFERENT manufacturer’s devices, then Universal Repeater should work. But behind the scenes, it’s really all about WDS compatibility, and whether you do or don’t have it.
Now there’s another little catch when it comes to TP-LINK. Most Universal Repeaters require you to specify the SSID, security information, etc., of the AP to which you are bridging. Then you establish another AP (the repeater) and specify its SSID, security information, etc. IOW, it’s entirely possible to have *different* SSIDs, security parameters, etc., on each side of the bridge. Whether that makes sense or is truly necessary is debatable. But most of the time that’s how universal repeater is implemented.
In the case of TP-LINK, at least based upon skimming their manual, I don’t see any means to supply the SSID, security information, etc., of the remote AP. That leads me to believe that in this particular case, TP-LINK requires its own AP and that of the remote AP to be the SAME (otherwise I don’t know how it would know how to connect to the remote AP, I don’t see any means to provide these details independently, or else I missed it).
So that’s the basic situation you find yourself in. If you have devices from the same manufacturer, the likelihood that any WDS-based solution will work is very good. If they are different manufacturers, the likelihood of compatibility is extremely remote. So you must turn to the “universal” solutions they offer (if any) because those are based on accepted standards.
Another “quirk” regarding some universal repeaters is that they sometimes don’t support WPA (not sure why, but I believe it has something to do w/ WPA key rotation), only WEP or WPA2. Frankly, WPA2 is a little better than WPA anyway, so if possible, I would try WPA2 (preferably WPA2/AES, to be precise) and see if that helps.

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