TP-Link Archer T4U Plus as AP


i bought a new fanless mini server for IPFire (current version V2.27-169). This one works : -)
For this i bought a USB WFI adapter from TP-Link with model Archer T4U Plus.

lsusb shows me this:
Bus 001 Device 004: ID 2357:0115 TP-Link 802.11ac NIC

The loaded drivers according to lsmod are:
88x2bu 3366912 0
cfg80211 1048576 1 88x2bu

In the IPFire WlanAP configuration i can configure 802.11gn and start the AP.
The WLAN SSID is visible and when trying to connect to it there is unfortunately no entry in the Blue access menu which i could allow access to.
When configuring 802.11ac the IPFire AP does not even start.

I looked in the IPFire system logs in the wireless logs but no error was visible to me.

Does anybody have a hint what could be wrong here ?

Best regards.

HT and VHT Caps missing or wrong.


good idea. In the datasheet it says:

Reception Sensitivity:
5 GHz:
11ac VHT80: -62dBm
11ac VHT40: -65dBm
11ac VHT20: -69dBm
11n HT40: -71dBm
11n HT20: -74dBm
11a 54Mbps: -77dBm
2.4 GHz:
11n HT40: -70dBm
11n HT20: -72dBm
11g 54Mbps: -75dBm
11b 11Mbps: -87dBm

So i put in
HT Caps: [HT20][HT40]
VHT Caps: [HT20][HT40][VHT20][VHT40][VHT80]

Does not work either.

On page - Wireless Access Point there are some more general examples for these parameters listed.
Looks like the challenge consists in the way to determine the actual capabilities on the USB Wifi Device and then derive the (V)HT Caps from there.
I am not that deep in the Wifi stack … are there commands to extract the available (V)HT Caps from or is this a property of the used Chip and needs to be extracted from the chip specification?

Best regards.

Did you configure a blue interface in setup?
Hostapd config only sets the wireless parameters. Somehow comparable to the properties of an ethernet cable. To have IP connections both sides of the line must activate the interface.

Yes, i have a red-green-blue setup here. IP address, netmask and gateway assigned properly as it was in the old installation. It really looks like the (V)HT Caps stuff is missing …

Two further ideas/insights:

  • iw list gives more information about the WiFi device. There should be a chapter Supported interface modes with line * AP.
  • The data sheet and User Manual of the device nowhere mentions AP mode. I think this adapter is for 802.11 clients only.

USB wifi devices do not support auto channel. Set up a fixed channel.

Btw AP mode is supported. It uses the Realtek RTL88x2BU driver.

Also try
HT caps: [RXLDPC][HT40+][SHORT-GI-20][SHORT-GI-40][MAX-AMSDU-7935][DSSS_CCK-40]

Here is the output of iwlist:

iwlist blue0 accesspoints

blue0 Interface doesn’t have a list of Peers/Access-Points

iwlist blue0 ap

blue0 Interface doesn’t have a list of Peers/Access-Points

On the github page GitHub - morrownr/88x2bu-20210702: Linux Driver for USB WiFi Adapters that are based on the RTL8812BU and RTL8822BU Chipsets - v5.13.1 it says it can work in AP mode. That was the reason i bought this model.

Setting up a fixed channel in the IPFore WlanAP UI is not that easy as it only offers me Automatic Channel Selection.

The HT/VHT Caps entries do not work on my side :expressionless:

This is not possible.

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As I wrote before, it will never work with automatic channel activated, unimportant what ht and vht caps are entered. This caps are all right for the realtek chipset and work.

Your entered caps are wrong because you define different bandwidth at the same time and the syntax therefor is not right because of the missing +/- for the frequency offset for the selected channel frequency.


No Channel selection possible in the IPFire WlanAP UI …

Never seen that so you have a different major problem.

It has to look like that:

Also you have to see a list of available channels at the bottom of that page:

I have restored the backup from the former IPFire instance in the meantime to get my configuration back. May that broke something … i will do a fresh install again and see if that changes something …

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Ok, have installed IPfire again in the meantime.
With the mentioned HT/VHT Caps parameters i can get 802.11gn to work. This time i also see entries in the Blue Access UI and the Wifi clients can connect to internet.

My conclusion about this is never use a backup from IPFire and restore it on a new IPFire instance with different hardware. Looks like it is only designed to be restored on the same hardware environment.

At least i have a working medium speed Wifi now.

When selecting or 802.11ac this still results in a not working Wifi AP.
If anyone has some ideas how to get 802.11ac mode running with IPFire …

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very few linux drivers support AC mode, ath10k being the most common. See the list here: en:users:drivers [Linux Wireless]

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This is not supposed to be and may be because of unsupportet vht caps. It’s alway tricky to find out the full selection of ht/vht caps for a device (exspecially usb devices). Try only this to see if it runs at ac:


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With these (V)HT Caps it still only runs in mode.

Looks like i have to wait a little bit more to use the 802.11ac mode.

Thank you all for your help so far as this led to a working AP on my side :slight_smile:

Remove the antenna pattern and the mpdu so only SHORT-GI-80 and RX-STBC-1 is left. I think it’s not good to choose a USB device. You would have been better to use a PCIe device.