How can I flush the DNS cache of a USG LITE 60AX?

Lohkamp

I had a client connected once directly via WLAN to the WAN gateway, an AVM FRITZ!Box which is now again connected to the Zyxel WLAN.

But nslookup of this client still lets the USG report [client].fritz.box with its old IPv6.
This is a show stopper, I expect I will have to reboot the USG LITE 60AX which breaks current internet connections.

For sure I rebooted my current other Windows client from which I issued the nslookup.

Zyxel_James

Currently, we can't flush the DNS cache for USG LITE 60AX.
However, I’m more curious about the issue you’re experiencing because USG LITE 60AX does not have IPv6 function.
So the client's DNS server is the USG LITE 60AX or the FRITZ!Box gateway? The FRITZ!Box is the front gateway of USG LITE 60AX or they're in different internet line?

Lohkamp

All VM (and other) clients use DHCP from the USG LITE 60AX and thus use its DNS service.
USG LITE 60AX has an AVM FRITZ!Box 6890 LTE at its WAN port (VDSL with automatic LTE fallback).

I connected an ASUS notebook ("ZenbookOL" as device name) once directly to the WLAN of the FRITZ!Box. So it occurred in its DNS server.
nslookup ZenbookOL [IP of FRITZ!Box]
still reported the ZenbookOL even after I deleted it from its internal email client list, so deleting/flushing the DNS server within the FRITZ!Box was also not working.

nslookup ZenbookOL (with USG LITE 60AX answering) only answered with the answer from the FRITZ!Box with its IPv6 address and as "ZenbookOL.fritz.box" and although the ZenbookOL was connected via WLAN only to the USB LITE 60AX and restarted several times, Firewall setup to "private network".

So, I informed my users and restarted both the FRITZ!Box and the USG LITE 60AX. Only after that the correct IPv4 (only, for sure) was answered by the USG LITE 60AX and I could access the notebook's SMB shares e. g.
USG LITE 60AX unfortunately provides no IPv6 to the internet, so from time to time and for testing I have to connect devices directly to the FRITZ!Box to have both IPv4 + IPv6 to the internet. But is needed only once every few months.