My router's IP (192.168.1.253 here) is sometimes banned. Using the official Android app on my smartphone. I think it happens when I arrive home and my phone connects to my wifi network, and the server ...
On my lab, I have 1 DNS server (named PI) that responds in IPv4 and IPv6 on all IPs (fe80:: and 2001::). This DNS server listens on port 53553. Another server (named Mul) forwards all requests to PI.