DHCP Lookup Failed 20x Chromebooks

[Alex0x7F]

Hi all,

 

I've ran in to an issue where around 10 Chromebooks disconnected from our WiFi, with the error 'DHCP lookup failed', theirs now around 20 Chromebooks doing this and I fear more may occur.

 

Another issue to side note, is our UniFi Wifi is currently running un-managed as the server that was running the UniFi controller failed a couple of weeks ago, and we are awaiting are replacement on site server. (Currently ticking over on an ancient on site server that's acting as DC for the time being). The access point's are still able to broadcast the network even though it's controller no longer exists.

 

Any pointers on where to start would be amazing, thanks!

[Oaktech]

We had this... Updating to the latest version of Unifi helped, but didn't totally fix it - we had to set the following:

 

DTIM is set to 3 in line with recommendations from Ubiquiti for modern devices.

LAN details have been entered.

Allow BSS transition with WNM switched on & PMF disabled.

Enabled GTK rekeying every 3600 seconds.

 

Been rock solid since.

 

Have you got a backup of the Unifi config that you can spin up on a workstation just to make those changes?

[bewlay51]

Hi All,

Interested in your comments about Chromebooks and WIFI issues. We have Unifi AP's and recently a lot of our Chromebooks fail to connect to the WIFI automatically. You have to connect manually and then they seem to be ok although a few may drop off intermittently, but connect again in no time manually. I updated the firmware on the AP's a few weeks ago, but I'm not sure if this is connected or not.

 

Is this a similar issue you have been seeing?

Thanks

John

[DGardiner]

how busy is your wifi network?

 

make sure auto optimise is off as this will disable broadcast traffic in high load scenarios.... this kills dhcp, not sure if you turn dhcp guarding on and configure if that overrides that but we just turned it off

[chazzy2501]

the DHCP issues occurred with various devices using certain network cards. This was particularly after upgrading to the Unifi NanoHD APs. Various things tried and firmware updates but they just don't like certain networks cards. I've had to replace 3 Wi-Fi laser printers as they refused to work well (replacing the unifi square ac, in the same locations) with the new nanos. Other older laptops (n only) I forced to use 5ghz in preference.

[Zoom7000]

This is an issue that is affecting several schools currently. If you log the call with Google Admin Support and share the case numbers with me, I can pass them on to my Google contacts for escalation.

[bewlay51]

Hi all,

Thanks,everyone for the update - a quick comment to DGardiner - this is not a busy WIFI, we only have around 70 devices at the moment. I'll take a look at the WIFI setting on the UNFI controller and turn off auto optimise.

 

Zoom7000 - I didn't know other schools are also having the same problem. I thought it might have been an update issue as everything seemed to be ok a few weeks ago. But within the last few weeks, I have updated the firmware on the AP's and I know Chrome OS has also been updated. I'll log a call with Google support and see let you have the call number.