Archer C7: no connection on WiFi 5G but only for Android

wifoIT · February 20, 2022, 11:13pm

Just to be clear: this has nothing to do with the (known) performance and instability issues of the Archer.

TL;DR: Android devices (even recent ones) can connect but not get internet access through the 5 GHz WiFi. They do not have issues with the 2.4 GHz interface, and other machines (e.g. Windows laptops) can connect and have internet access through the 5 GHz interface.

Hello, I am getting crazy about this problem. I understand this is gonna be a tricky and weird problem, so please bear with me. I will try to start generic and then we can pinpoint the problem step by step, feel free to ask questions or config files.

I have a TP-Link Archer C7 V2 running OpenWrt 21.02.1 r16325-88151b8303 / LuCI openwrt-21.02 branch git-21.295.67054-13df80d. This is my home router, I haven't touched the config for a while except minor tweaks. I think the problem started appearing when upgrading from 20.something to 21.02 but cannot be 100% sure about this, all I know is that everything was working fine until a few months ago.

Long time ago I set up a funny configuration: by playing around with VLANs I created two interfaces: "LAN" and "DMZ". LAN devices can access WAN and DMZ but DMZ devices can only access WAN. DHCP is enabled on both networks (some are static addresses) and DNS is provided to both networks. I have even configured some tagged ports of the switch so that 2 ethernet ports are LAN and 2 are DMZ. Notice that, via ethernet cable, everything works as intended.

Then there is the two WiFi interfaces: radio0 (5 GHZ, Qualcomm Atheros QCA9880 802.11nac) and radio1 (2.4 GHZ, Qualcomm Atheros QCA9880 802.11nac).

radio0 provides the GUEST WiFi and is attached to DMZ
radio1 provides the HOME WiFi and is attached to LAN

Both use WPA3 through WolfSSL and various security optimizations (KRACK countermeasures etc). GUEST WiFi works perfectly but HOME does not: my Android devices see the network, manage to connect and receive an IP in the correct range, they are also automatically configured with the right DNS and gateway. However, they report "no connection" and do not resolve any address.

IPV6 is disabled everywhere

Can you help me pinpoint the issue? Any help would be greatly appreciated

anon89577378 · February 20, 2022, 11:25pm

SSH in to the router and run cat /etc/config/wireless.

Redact the passwords in the "option key" sections.

Post the results in preformatted text, by using the icon highlighted in red...

wifoIT · February 20, 2022, 11:30pm

OK thanks, here you go:

root@ArcherC7v2-1:~# cat /etc/config/wireless

config wifi-device 'radio0'
	option type 'mac80211'
	option hwmode '11a'
	option country 'CH'
	option ff '1'
	option compression '1'
	option turbo '1'
	option channel '120'
	option htmode 'VHT40'
	option txpower '23'
	option path 'pci0000:00/0000:00:00.0'

config wifi-device 'radio1'
	option type 'mac80211'
	option hwmode '11g'
	option htmode 'HT20'
	option country 'CH'
	option channel '8'
	option txpower '20'
	option path 'platform/ahb/18100000.wmac'
	option legacy_rates '1'
	option cell_density '0'

config wifi-iface 'wifinet0'
	option device 'radio1'
	option mode 'ap'
	option network 'lan'
	option key 'SAFEPASS'
	option encryption 'sae-mixed'
	option ssid 'HOMEWIFI'
	option short_preamble '0'
	option wpa_disable_eapol_key_retries '1'
	option ieee80211w '1'

config wifi-iface 'wifinet1'
	option device 'radio0'
	option mode 'ap'
	option network 'dmz'
	option key 'EASYPASS'
	option encryption 'sae-mixed'
	option ssid 'GUESTWIFI'
	option short_preamble '0'
	option wpa_disable_eapol_key_retries '1'
	option isolate '1'

root@ArcherC7v2-1:~#

anon89577378 · February 20, 2022, 11:42pm

Channel 120 is a DFS (radar channel) in most geographic locations...

I would suggest using 36 to 48, or 149 to 161.

wifoIT · February 20, 2022, 11:59pm

OK, will do. Any other idea?

anon89577378 · February 21, 2022, 12:02am

As mentioned, I would try changing the 5 GHz channel.

psherman · February 21, 2022, 1:31am

Try using wpa2 and not mixed mode.

slh · February 21, 2022, 5:10am

Just a weird idea, but perhaps also give the openssl variant of wpad a try (instead of wolfssl). Wolfssl caused issues with hostapd in the past, while those should be solved (at least there don't seem to be open issues remaining), it's probably good to rule this out as well.

anon89577378 · February 21, 2022, 5:40am

I am using a C7 V2 as well, and no issues with wolfssl.

wifoIT · February 21, 2022, 11:21pm

Hello again and thanks, unfortunately didn't work out. First of all an errata to what I wrote in the first post (unfortunately I cannot edit it anymore): it is not true that Android devices get assigned a correct IP, I had actually configured it manually exactly because they, in fact, don't. They see the network and when they try to connect I can see the device connecting from LuCi but the Android device gets stuck on "Receiving IP address..." and nothing happens. It almost looks like DHCP is not working (only for Android devices and only on that interface).

What I did:

changed the channel of the GUEST WiFi to 36 (but notice that GUEST is the WiFi that is working correctly, the one that gives me headaches is the HOME one)
tried WPA2-PSK instead of sae-mixed
replaced wpad-wolfssl with wpad-openssl

Nothing of these worked. Any idea?

anon89577378 · February 22, 2022, 6:17am

Post your new wireless configs .

wifoIT · February 22, 2022, 5:25pm

OK thanks, here you go:

root@ArcherC7v2-1:~# cat /etc/config/wireless 

config wifi-device 'radio0'
	option type 'mac80211'
	option hwmode '11a'
	option country 'CH'
	option ff '1'
	option compression '1'
	option turbo '1'
	option htmode 'VHT40'
	option txpower '23'
	option path 'pci0000:00/0000:00:00.0'
	option channel '36'
	option cell_density '0'

config wifi-device 'radio1'
	option type 'mac80211'
	option hwmode '11g'
	option htmode 'HT20'
	option country 'CH'
	option channel '8'
	option txpower '20'
	option path 'platform/ahb/18100000.wmac'
	option legacy_rates '1'
	option cell_density '0'

config wifi-iface 'wifinet0'
	option device 'radio1'
	option mode 'ap'
	option network 'lan'
	option key 'SAFEPASS'
	option ssid 'HOMEWIFI'
	option wpa_disable_eapol_key_retries '1'
	option ieee80211w '1'
	option encryption 'psk2+ccmp'

config wifi-iface 'wifinet1'
	option device 'radio0'
	option mode 'ap'
	option network 'dmz'
	option key 'EASYPASS'
	option encryption 'sae-mixed'
	option ssid 'GUESTWIFI'
	option short_preamble '0'
	option wpa_disable_eapol_key_retries '1'
	option isolate '1'

anon89577378 · February 22, 2022, 9:56pm

I would change this to WPA2-PSK as well.

Change this to one of the non-overlapping channels such as 1, 6, or 11.

Stefan1 · February 23, 2022, 6:36am

I am not familiar to the options ff, compression and turbo. They are not listed in https://openwrt.org/docs/guide-user/network/wifi/basic.

wifoIT · February 23, 2022, 8:40am

OK I'll try, but can you please argument more on how this could possibly be related to a (seemingly) DHCP or routing problem on the HOME wifi that only affects Android devices? Is there some known issue of interoperability with, I don't know, the radio driver or whatever?

I will try also to remove these options when I come back home and report on the outcome. Frankly I don't even remember where they come from lol

anon89577378 · February 23, 2022, 9:19am

The Android devices may not be able to connect using SAE-mixed mode.

Many can't.

Changing to a non-overlapping 2.4 GHz channel (1, 6, or 11) will give you better performance.

wifoIT · February 23, 2022, 10:14pm

Yes OK but as I wrote before Android devices have no problems connecting to the GUEST WiFi, which is also using sae-mixed. So I really don't think this is related. And regarding the channels, I chose those because they were looking less crowded in my area (I did a scan). Regardless, I have adopted all these suggestions and nothing changed, but thanks for trying.

Also disabled these options but nothing changed. My wireless conf file now:

root@ArcherC7v2-1:~# cat /etc/config/wireless 

config wifi-device 'radio0'
	option type 'mac80211'
	option hwmode '11a'
	option country 'CH'
	option htmode 'VHT40'
	option txpower '23'
	option path 'pci0000:00/0000:00:00.0'
	option channel '36'
	option cell_density '0'

config wifi-device 'radio1'
	option type 'mac80211'
	option hwmode '11g'
	option htmode 'HT20'
	option country 'CH'
	option channel '8'
	option txpower '20'
	option path 'platform/ahb/18100000.wmac'
	option legacy_rates '1'
	option cell_density '0'

config wifi-iface 'wifinet0'
	option device 'radio1'
	option mode 'ap'
	option network 'lan'
	option key 'SAFEPASS'
	option ssid 'HOMEWIFI'
	option wpa_disable_eapol_key_retries '1'
	option ieee80211w '1'
	option encryption 'psk2+ccmp'

config wifi-iface 'wifinet1'
	option device 'radio0'
	option mode 'ap'
	option network 'dmz'
	option key 'EASYPASS'
	option encryption 'psk2+ccm,p'
	option ssid 'GUESTWIFI'
	option short_preamble '0'
	option wpa_disable_eapol_key_retries '1'
	option isolate '1'

Stefan1 · February 23, 2022, 10:24pm

Ok, your HOMEWIFI uses 802.11w. Try to not use this one. If that does not help, temporarily switch Homewifi and guestwifi in order to see whether the problem is related to your network config or to your wireless config..., meaning temporarily assign homewifi to dmz and guestwifi to lan. What happens then ?

anon89577378 · February 23, 2022, 11:16pm

This is incorrect.

Should be psk2+ccmp

wifoIT · February 23, 2022, 11:54pm

Ooops, well spotted, thanks. Still, nothing changes.

Tried disabling 802.11w, nothing changes. I will try later to switch the two interfaces.

Bah, this is really frustrating...