Hi  @cbpw1 

What's the unknown domain name?

The info you shared is displayed as below:

  @Vincent-TP 

Yes, that's correct.  It's a foreign character set that is it pinging, hence why it displays incorrectly in the PCAP trace.  Regardless it should not be trying DNS lookup for anything

Trace from Pihole. Note it also displays foreign character set.  

Wireshark full trace with response of 'No such name' from the DNS server (.100 address)

Hi  @cbpw1 

For better understanding, please let us know the following info:

1. What devices are the IP addresses 192.168.0.100 and 192.168.0.6 for?

2. How is the Wireshark PC connected to the EAP network?

  @Vincent-TP 

192.168.0.100 is my piHole DNS resolver (internal)

192.168.0.6 is the IP addres of the EAP610

The PCAP tracefile was generated by the Omada controller and loaded into Wireshark to analyze

Hi  @cbpw1 

Thanks for the info.

EAP seldom send DNS requests proactively; we suspect it was a client that is connecting to the EAP doing this.

You may test like this:

Disconnect all clients from the EAP and see if the devices will send the request.

In the meantime, if swap the two EAPs location, what will happen?

  @Vincent-TP 

It is not another device. I switched off the radios on the EAP and the DNS requests keep being called.

By the way, in networking, Devices do not relay DNS requests on an EAP's IP address to make calls. This is a direct call from the EAP610.

I have windows machines constantly pinging telemetry and android outlook client the same.  My router will also ping an address to check connectivity, so this is not an unknown situation, but I can control those behaviours through configuration.

I swapped the units and the same behaviour is occurring.

This is either a faulty unit (highly unlikely) or a deep rooted software setting in the EAP which is testing connectivity, but the destination host is invalid. 

Is there a setting in the CLI that can control this? Is it something that should only be there in standalone mode?  

I'm frustrated that there is no obvious GUI option and the CLI is limited in documentation on this.

  @cbpw1 

Thank you so much for taking the time to post the issue on TP-Link community!
To better assist you, I've created a support ticket via your registered email address, and escalated it to our support engineer to look into the issue. The ticket ID is TKID241214068, please check your email box and ensure the support email is well received. Thanks!
Once the issue is addressed or resolved, welcome to update this topic thread with your solution to help others who may encounter the same issue as you did.
Many thanks for your great cooperation and patience!