Using a Wifi adaptor as a client and an AP at the same time

[David Brown]

In the interest of proving that Usenet is not dead, and encouraging
discussion, I'll ask a question!

Is it possible to use a single Wifi adaptor as a client on one Wifi
network / SSID while also acting as an AP for a dedicated local Wifi
network / SSID?

I appreciate that this is no problem if there are separate radios (such
as using 2.4 GHz for the client and 5 GHz for the AP), or when using the
more advanced Wifi adaptors often found in upmarket routers.

The expected use here would be with a cheap and simple single-radio 2.4
GHz adaptor.

David

[Marco Moock]

Post by David Brown
The expected use here would be with a cheap and simple single-radio
2.4 GHz adaptor.

IIRC that won't work.
Even operating a dual band adapter as client and AP at the same time
maybe doesn't work because mostly it is not intended to be used that
way and the firmware on it might not be able to handle that.

[Dan Purgert]

Post by David Brown
Is it possible to use a single Wifi adaptor as a client on one Wifi
network / SSID while also acting as an AP for a dedicated local Wifi
network / SSID?

Yes - see products like the Ubiquiti Unifi lineup that offer "Wireless
Uplink". Though, these are a product, and I think you might be more
asking from the perspective of using a regular PC...

Post by David Brown
The expected use here would be with a cheap and simple single-radio 2.4
GHz adaptor.

Nope, you'll just be able to repeat the existing SSID on the existing
channel.

[David Brown]

Post by Dan Purgert

Post by David Brown
Is it possible to use a single Wifi adaptor as a client on one Wifi
network / SSID while also acting as an AP for a dedicated local Wifi
network / SSID?

Yes - see products like the Ubiquiti Unifi lineup that offer "Wireless
Uplink". Though, these are a product, and I think you might be more
asking from the perspective of using a regular PC...

Yes, these devices have more than one radio which can be controlled
independently (that's common for devices intended as AP's for lots of
clients).

The target use would be an embedded Linux card rather than a PC, but one
where I have full control of the software and the setup for the device.
I'd have influence over the choice of Wifi adaptor, but not a free
choice (if the hardware needed is too expensive, we'll have to think of
a different solution).

Post by Dan Purgert

Post by David Brown
The expected use here would be with a cheap and simple single-radio 2.4
GHz adaptor.

Nope, you'll just be able to repeat the existing SSID on the existing
channel.

I know I can do that. And I know the radio can only operate on one
channel at a time, so the local AP would have to share the channel with
the external AP. (And I know that sharing a channel like this would not
be ideal.)

I have had one Wifi adaptor acting as several different APs / SSIDs, on
different nets, but all on a single channel.

[Dan Purgert]

Post by David Brown

Post by Dan Purgert

Post by David Brown
Is it possible to use a single Wifi adaptor as a client on one Wifi
network / SSID while also acting as an AP for a dedicated local Wifi
network / SSID?

Yes - see products like the Ubiquiti Unifi lineup that offer "Wireless
Uplink". Though, these are a product, and I think you might be more
asking from the perspective of using a regular PC...

Yes, these devices have more than one radio which can be controlled
independently (that's common for devices intended as AP's for lots of
clients).

They've only got one, it can just do both bands (well, some may have
multiple chips, haven't taken one apart in a few years to see what all's
inside :) )

Post by David Brown
The target use would be an embedded Linux card rather than a PC, but one
where I have full control of the software and the setup for the device.
I'd have influence over the choice of Wifi adaptor, but not a free
choice (if the hardware needed is too expensive, we'll have to think of
a different solution).

Most APs these days are embedded linux, so it's definitely doable, with
the right chipset / driver / etc.

Not so much that it's necessarily "expensive", but that it's a "niche"
type feature in the consumer market, which might make finding the right
chip fun.

Post by David Brown

Post by Dan Purgert

Post by David Brown
The expected use here would be with a cheap and simple single-radio 2.4
GHz adaptor.

Nope, you'll just be able to repeat the existing SSID on the existing
channel.

I know I can do that. And I know the radio can only operate on one
channel at a time, so the local AP would have to share the channel with
the external AP. (And I know that sharing a channel like this would not
be ideal.)
I have had one Wifi adaptor acting as several different APs / SSIDs, on
different nets, but all on a single channel.

Oh? Which chipset is that? I've not seen multiple SSIDs supported from
the same chip in the consumer kit I've got laying about (or maybe it's
less "the chip" and more hostapd...?)

[David Brown]

Post by Dan Purgert

Post by David Brown
I have had one Wifi adaptor acting as several different APs / SSIDs, on
different nets, but all on a single channel.

Oh? Which chipset is that? I've not seen multiple SSIDs supported from
the same chip in the consumer kit I've got laying about (or maybe it's
less "the chip" and more hostapd...?)

I've done it with OpenWRT on a TP-Link router - cheap off-the-shelf
hardware. With AP's, you can set up as many as you like when they all
go on the same channel.

You get two "wifi-device", one for 2.4 GHz and one for 5 GHz, which
includes settings like the channel. But you can have as many
"wifi-iface" setups as you like for each radio, with different AP SSIDs,
passwords, and networks. That's how you set up things like an
"internal" network and a "guest" network from the same device.

[Dan Purgert]

Post by David Brown

Post by Dan Purgert

Post by David Brown
I have had one Wifi adaptor acting as several different APs / SSIDs, on
different nets, but all on a single channel.

Oh? Which chipset is that? I've not seen multiple SSIDs supported from
the same chip in the consumer kit I've got laying about (or maybe it's
less "the chip" and more hostapd...?)

I've done it with OpenWRT on a TP-Link router - cheap off-the-shelf
hardware. With AP's, you can set up as many as you like when they all
go on the same channel.

Yeah, but that's (to my knowledge, anyway) a different chipset than what
one can normally get in a USB stick (or replacement wifi card for a
laptop -- i.e. "in the consumer market").

Then again, things may have changed, and I'm way off base now (used to
be that way back in 2017/18 anyway).

[David Brown]

Post by Dan Purgert

Post by David Brown

Post by Dan Purgert

Post by David Brown
I have had one Wifi adaptor acting as several different APs / SSIDs, on
different nets, but all on a single channel.

Oh? Which chipset is that? I've not seen multiple SSIDs supported from
the same chip in the consumer kit I've got laying about (or maybe it's
less "the chip" and more hostapd...?)

I've done it with OpenWRT on a TP-Link router - cheap off-the-shelf
hardware. With AP's, you can set up as many as you like when they all
go on the same channel.

Yeah, but that's (to my knowledge, anyway) a different chipset than what
one can normally get in a USB stick (or replacement wifi card for a
laptop -- i.e. "in the consumer market").
Then again, things may have changed, and I'm way off base now (used to
be that way back in 2017/18 anyway).

That's possible.

I guess I'm just going to have to try some experiments :-)