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DHCP/wifi issues (pi4, buster)

Posted: Sun Jan 19, 2020 5:18 pm
by dankcushions
For some reason my new pi4 seems to be struggling with connecting the wifi. At one point I was able to connect very intermittently, but it was quite laggy through SSH, and now following a reinstall I'm not connecting at all. because of this i can't paste any output to here, but I can access the terminal directly. some findings so far:


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in /var/log/syslog dhcpd gives a couple of "time out" messages, before forking to the background.

if i run

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iwlist wlan0 scan
i can see that said 2g wifi network is on channel 11, quality 48/70, signal level=-62dBm. not sure if those are deal-breakingly bad? i have plenty of other wifi devices in the same location that have good signal.

i have no idea how to troubleshoot this. please help! :)

Re: DHCP/wifi issues (pi4, buster)

Posted: Sun Jan 19, 2020 5:28 pm
by epoch1970
48/70 is not great but I can’t recall if that is above or below critical.
Do you need scan_ssid? wrote: # scan_ssid:
# 0 = do not scan this SSID with specific Probe Request frames (default)
# 1 = scan with SSID-specific Probe Request frames (this can be used to
# find APs that do not accept broadcast SSID or use multiple SSIDs;
# this will add latency to scanning, so enable this only when needed)

Re: DHCP/wifi issues (pi4, buster)

Posted: Sun Jan 19, 2020 5:34 pm
by dankcushions
Do you need scan_ssid?
probably not! i removed that line and rebooted... still the same dhcpd timeout

Re: DHCP/wifi issues (pi4, buster)

Posted: Sun Jan 19, 2020 5:48 pm
by epoch1970
I would try to “denyinterfaces wlan0” in dhcpcd, reboot. Once rebooted, from the command-line, as root, run wpa_supplicant on the interface, in the foreground, in debug mode. You’ll see if authentication succeeds or fails. ... .8.en.html

If it succeeds, reinstate wlan0 in dhcpcd, reboot and try again. If DHCP fails, perhaps the DHCP server rejects the requests (unlikely) or the wireless signal is too weak.

Also, make sure you are using a proper PSU to power the Pi. If the computer has power issues all sorts of random things may happen.

Re: DHCP/wifi issues (pi4, buster)

Posted: Sun Jan 19, 2020 10:30 pm
by dankcushions
welp, running in debug mode made it very obvious where my problem was - I had a typo in my network name :oops:

it seems to be stable right now, with none of the lag before, but quite what caused that i don't know! i'm using an official power supply but i am running inside the aluminium FLIRC case that may be affecting the signal quality.

so far, so good! thanks for the help!