Networking – WIFI – Single radio acting as AP and AP Client simultaneously

wireless-access-pointwireless-networking

Is it possible for a single (802.11 b,g,n,ac) WIFI radio to act as both an Access Point and Access Point client simultaneously – if so how, and are there examples of software that allow this (I'm particularly interested in Linux, but any OS that does it would evidence it can be done, and thus valuable to me). If not, why not?

For the sake of clarity, I'm not talking about a radio acting as either one or the other, and switching roles at different times, nor am I talking about 2 radios on different frequencies doing different jobs. I'm also not interested in ad-hoc mode unless this can be leveraged to appear as an AP and AP client to other AP's and AP clients respectively.

Best Answer

Modes of operation

The access point, providing WiFi is usually called AP, while the client is called STA.

It's possible to configure your device as a repeater or as something I will call a wireless-wireless router, since I can't find a consensual name.

  • The repeater will bridge (transmit all Ethernet packets between STA and AP sides), using the existing network infrastructure for DHCP, routing, ...
  • The wireless-wireless router will route selected packets between the STA and the AP side, providing DHCP and NAT.

The wireless-wireless router will need more configuration, but will only transmit packet as needed.

Hardware compatibility

Some wireless adapter are not able to use STA and AP mode at the same time (some adapters even can't serve as AP).

If you've got an adapter at hand, iw list can be used to establish if it is able to do act as an client and access point at the same time. As said in this question, you must look for the valid interface combinations part of the iw list command.

About the single 802.11 a/b/g/ac radio

Since 802.11 b/g/n uses 2.4 GHz and 802.11 a/ac uses 5 GHz, the adapter will need at least 2 phy, and will probably need to be configured as 2 separate access point, from the Linux point of view.

About the software

They are plenty of dedicated Linux distribution targeting small computers and WiFi routers, here are some examples:

All the previously listed distributions have their own flag on superuser.

About the WRT name

Interestingly, a lot of router-targeted Linux distributions contain the WRT word, since they started as an alternative firmware for the venerable LinkSys WRT54G.

Related Question