kirkt
1
I have my HAP AC connected via one of the LAN ports to my LAN/modem.
The HAP AC has a fixed IP inside my LAN. My modem is now the DHCP server on my LAN.
All wifi clients connect to the net/LAN without any problem in this setup.
But I can’t check for new updates of the HAP AP like this 
The HAP AP only got a LAN IP now but no gateway and no dns server configured.
How can I configure DNS/Gateway without messing up my current setup?
Without seeing your config, it’s difficult to say for sure, but I suspect you just need to add a route
/ip route
add distance=1 gateway=192.168.0.1
kirkt
3
That fixed it.
After that I only needed to set DNS in: /ip dns, and now I can check for RouterOS updates.
Thanks! 