1

I am aware that the question is asked here already, e.g.

  1. Can RPi4 run simultaneously on dual band (WiFi 2.4GHz / 5GHz)?
  2. Is it possible to use Raspberry Pi 3 B+ Dual Band WiFi Simultaneously?

But I have several problems with it. The sudo iw list lists:

--- snip ---
valid interface combinations:
     * #{ managed } <= 1, #{ P2P-device } <= 1, #{ P2P-client, P2P-GO } <= 1,
       total <= 3, #channels <= 2
     * #{ managed } <= 1, #{ AP } <= 1, #{ P2P-client } <= 1, #{ P2P-device } <= 1,
       total <= 4, #channels <= 1
--- snip ---

Than I can use either a P2P-deviceor a AP device. But honestly I have no clue what is the main difference between them. Does it mean I cannot use any longer RaspAP?

Beside the theoretical issue I have no clue how to set up the Raspberry serving on these different bands. The instructions of link1 failed. Issuing a sudo wpa_cli I get

wpa_cli v2.8-devel
Copyright (c) 2004-2019, Jouni Malinen <j@w1.fi> and contributors

This software may be distributed under the terms of the BSD license.
See README for more details.


Selected interface 'p2p-dev-wlan0'

Interactive mode

<3>CTRL-EVENT-SCAN-RESULTS
<3>CTRL-EVENT-SCAN-RESULTS
<3>CTRL-EVENT-SCAN-RESULTS
> p2p_group_add freq=5
FAIL
<5>P2P: Failed to add group interface

Any ideas how to continue with a proper config?

3

I reference my answer to the question you have quoted as first link:

  1. Can RPi4 run simultaneously on dual band (WiFi 2.4GHz / 5GHz)?

You wrote:

Any ideas how to continue with a proper config?

You don't tell us what this proper config should be. If you mean to have a dual band access point, then I quote the second sentence behind the link:
If one interface is used as access point (AP) you can only use one band.
If you need dual band then you have to use an additional USB/WiFi dongle.

Than I can use either a P2P-device or a AP device.

This is not right. You have two combinations. The first is:

 * #{ managed } <= 1, #{ P2P-device } <= 1, #{ P2P-client, P2P-GO } <= 1,
   total <= 3, #channels <= 2

and the second combination is:

 * #{ managed } <= 1, #{ AP } <= 1, #{ P2P-client } <= 1, #{ P2P-device } <= 1,
   total <= 4, #channels <= 1

With this one you can have ONE #{ P2P-device } together with ONE #{ AP } but you can only use #channels <= 1.

For example it is not possible to have a P2P-GO (group owner) together with an AP. There is no combination for it available.

Than I can use either a P2P-device or a AP device. But honestly I have no clue what is the main difference between them.

There are some different WiFi connections possible. The most used one is a well known access point to which managed clients (stations) can connect. Then you often find Wi-Fi direct that is mostly used by smartphones to connect direct for example to printer (or other devices). Wi-Fi Direct is completely different from an access point and managed with the P2P-device, P2P-client and P2P-GO. An example you can find at Setting up Wifi direct (wifi p2p) and DHCP server.

Does it mean I cannot use any longer RaspAP?

RaspAP has nothing to do with this discussion about configuring WiFi interfaces. I haven't used it but as far as I know it is a script that configure the interfaces for its use case and encapsulated it to the user so he doesn't have the burden to do it. If you want to have a different setup, you have to modify RaspAP.

The instructions of link1 failed.

I have just updated and tested the proof of concept (it isn't more) behind the link and can confirm that it works as described. Please check, what you have made different. Start with a fresh flashed image.

5
  • Thx for your answer which is quite ellaborate. First of all I think I need more understanding :-/ A P2P-device is a device which directly connects with the Raspberrry(RB). But I don't understand what's the diff to connection as AP? Clients (e.g. mobiles, vaccum cleaner) can connect as well. For P2P-device does it mean that I need to configure it directly on the RB? From what I understand in your response and the follow-up link than I cannot set up a DHCP-server since this requires a P2P-GO but this won't be available if running on dual band. Am I correct? – LeO Sep 24 '20 at 17:46
  • @LeO An AP is just another WiFi connection method and protocol than a Wi-Fi direct connection. There are other methods/protocols e.g. pure peer to peer using IBSS. To understand its differences you have to know how they work. I cannot explain its specifications here because it fills pages. Look at Wikipedia and for details at the RFCs (technical specification) of the protocols. If you want to have a P2P-device you have to configure it on the RasPi. I don't believe that it is supported by RasAP. – Ingo Sep 24 '20 at 19:39
  • @LeO Please don't think about dual band. You cannot run an AP together with a P2P-GO. When running a P2P-GO without an AP (not possible) you can use two bands, e.g. a managed client connection to a remote access point with a channel on the 2.4 GHz band and a P2P-GO with a channel on the 5 GHz band. This is not a classic dual band connection with two client connections. It is one client uplink connection and one active "server" connection that you can connect. – Ingo Sep 24 '20 at 19:39
  • Hmmm.... Honestly don't know what to do next. I highly appreciate your response and details. But it seems like that I cannot grasp the pro and cons for AP vs P2P-device. Yeah they are different and running one channel. Beside your great answers for clarification I than still have to implement it. I guess I'll buy a 2.4GHZ USB stick which costs around 10€ and this would save a lot of headaches. Well despite that I need to configure it ;-) – LeO Sep 25 '20 at 6:33
  • 1
    @LeO I don't know what you want to achieve but with standard use cases it is useful to use an access point and if really required, with an additional USB/WiFi dongle. – Ingo Sep 25 '20 at 8:19

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