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I want to make an RPI 3 model b wifi repeater/bridge. I want to make it work without ethernet cable. I've found a few topics and guides but most of them are eth0 -> wlan0 or outdated or simply never worked. The first problem I faced that the PI says I can not put the adapter to master/ap mode but I am SURE about the dongles support it. I tried with 3 different adapters on Windows, all of them worked but none of them on the PI but the "AP" mode is supported as shown by the "iw list" command. So I am totally disappointed.

Also tried bridge-utils without any success:

command: 

brctl addbr bridge0; brctl addif bridge0 wlan0

result: 

can't add wlan0 to bridge bridge0: Operation not supported

So I'm looking for a detailed UP TO DATE guide to set up a wifi repeater on the pi.

Francesco Gusmeroli
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sOnt
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1 Answers1

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Note: the typical instructions about building a Wifi repeater are using IPv4 routing, and IPv4 NAT in particular. So these are in fact "Wifi routers". I understand this question to either wanting a Wifi-to-Wifi bridge, or a Wifi repeater, but not a Wifi router.

Wifi repeaters are, as their name implies, repeaters, but they aren't bridges. This is in this case a crucial distinction. You can't bridge (on the data link layer 2) an IEEE 802.11 station to an IEEE 802.11 AP-mode (Access Point) station: the reason is because IEEE 802.11 WLAN has only a three MAC address model standardized, and that is just sufficient to send and receive frames end-to-end between an IEEE 802.1-compatible network via an AP to a (non-AP) station. Put it differently: you cannot address different MACs behind a non-AP station. You can only send to the non-AP station itself. The fourth MAC address needed is missing.

And that's the reason why you get the rather terse or cryptic error message when trying to add a WLAN non-AP station to a bridge. That's also the reason why you can find so many recipes for bridging eth0 to AP-mode wlan0, but neither station wlan0 to eth, nor wlan0 to AP wlan1.

In contrast, wifi repeaters work within the MAC sublayer, in contrast to bridges, which work within the data link layer, but above the different IEEE 802.x MAC layers.

Interestingly, the Wifi IEEE 802.11 MAC protocol would have room for the fourth address, but as it's not standardized, so chips will probably not support it, and drivers even less so.

TheDiveO
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