In a nutshell: my laptop and desktop cannot resolve my own sub-domain pointing back to my external IP via WiFi - but they can if they are connected via cable. WTH?
I am experiencing a strange DNS issue that appeared more or less over night (no issue before a vacation, issue after vacation). Maybe someone’s got an idea?
I run a Pihole for DNS and a Nextcloud server behind a DSL router/modem which updates my IP to a subdomain I use for my Nextcloud for internal and external access. In the internal network I am working with a desktop and a laptop. Both can access the web and internal net via WiFi or LAN. So far so good.
Since I returned from traveling (simply indicating that a change must have happened while I was away), the external domain, say nextcloud.foobar.com, can only be accessed by the laptop and the desktop when connected via cable to the DSL router/modem. Not, if they are connected via WiFi, to the same DSL router/modem.
Until now, I have found out that it’s not an issue related to the machine (same problem on both laptop and desktop) or operating system/install (same problem on both Windows and Linux on both machines). The interesting thing is that I am able to reach my own external IP and my server through that IP over WiFi, but not via the domain. So it should be a DNS problem, or, more specifically, a newly occurred difference in how the DSL router handles DNS on WiFi vs. on LAN. It might have something to do with that I have automatic updates on on the Pihole server and the DSL router.
I wondered if anyone here would have an idea on what to try next. Maybe this sounds familiar to someone.