Hi  @Theedoek 

@Julian2111 

 Thanks for posting here.

ipconfig/all, what's the DNS server address? Is it the LAN interface IP? Or a public IP? Could you please share a screenshot?

To understand the situation better, please also share a screenshot of the LAN DNS settings page. Thanks.

  @Vincent-TP Local IP adresses
VLAN1: 172.16.250.0 /24 [Gateway+DNS Server IP is 172.16.250.1]
VLAN2: 172.16.55.0/25 [Gateway+DNS Server IP is 172.16.55.1]

That is the screenshot of the non working Lan-DNS thinggy

The device is resolve it to is in the "main network", I tested it right now on my phone and laptop, on the IoT network I always get my public IP back (because the domain I use is resolved from external to my ip), instead of 172.16.250.4, in the 172.16.250.0/24 network I get 172.16.250.4

  @Vincent-TP I don't understand what you mean by a screenshot of it, do you mean with all Lan-DNS domains set up? If so I would like to share it as a private message since it is a domain that is publically reachable as well. 

And here are the screenshots of ipconfig /all