Noting this as I can see that this happened in June and I suspect the DNSSEC keys have been updated incorrectly again. The connectivity checker stopped working for me at around 1:30 GMT/UTC today. I use my home AdGuard installation as a private DNS server and that was having problems resolving the domain, as is Quad9 and Mullvad DNS. Cloudflare and Google are currently working.
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Yes I can confirm the issue. whois does indicate that a change was made at 2025-12-29T09:50:10+1:00. Here is the full output I see:
Domain: kuketz.de
Nserver: root-dns.netcup.net
Nserver: second-dns.netcup.net
Nserver: third-dns.netcup.net
Dnskey: 257 3 8 AwEAAcNnMDZXTdYpO/0RbH0Mhm+voNugPUzYxB3+SZeDfymQL9gwJcQFMEP+B1X0hG9t9o14gruy2cTdWXKWiFhfM/jJhkh4q1AjewNpwlc5TAh07c4ushURx6KAivlkM6W4ipshn4jxMMBUfiM3wfN7jpRQfnBx89WCw5zSnXYIN3G/gQOH23kyo2YHko/wcxSKl0Qb4c/rryyhd0EyHrBfozwExsnUpTDqdwSc1ui6kIHwqAJCYCAbsZYt9LW+wIkyBI9ci2eo3rL3FSaunDGUfHmB+xcTOVkkAKv8j6mWBTU2Bhyi13sJ/iu5q74TbM85cvsId+GA+6ZTc33A+W9vZmU=
Status: connect
Changed: 2025-12-29T09:50:10+01:00
FYI all is working again within the past week as far as I can observe.
Yet again an issue with captiveportal.kuketz.de? My connectivity checks just started warning me I have “no internet” (but of course I do 
).
As before, whois kuketz.de seems to report a recent change: Changed: 2026-06-17T12:00:11+02:00?
I expected it in mid-April, unless we missed it (standard lifecycle of an ACME SSL certificate).
I switched from cloudflare to quad9 as the dns provider for my LAN, and the issue went away. So it must be something with cloudflare not resolving captiveportal.kuketz.de after whatever change from Kuketz was implemented? Anyway, I am counting my issue as a “false positive”.
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I have base.dns.mullvad.net as my private DNS and haven’t seen anything, which would suggest it’s Cloudflare in your case rather than Kuketz this time.
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Just noting there are a few others that are having issues, @CodeSalat and @lbr31 in this thread. I’ll let them post here what dns settings may be used by their phone if manually set or what their dhcp server / router are providing clients as the default dns settings.
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I didn’t have any problems with dns.keweon.center either.
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I am not sure if the Cloudflare issue is regional or broader. Are you, @dwainzwerg or @simongreenwood willing to test? Set 1.1.1.1 as your DNS, then disconnect / reconnect to make sure applied and see if connectivity check passes?
Note: I think if you report on if you can or can’t ping captiveportal.kuketz.de from any device not just from iodéOS when Cloudflare is the DNS then it would be a good help?
It doesn’t work for me with Cloudflare either (Germany).
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Cloudflare works on my phone, and I also tested Quad9 as a double blind.
I’ll have a test on a laptop and see if there are any clues, but it’s looking like an issue with Cloudflare in some regions or ISPs.
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Ah, this is interesting, using dnslookup on the command line (DoH lookup tool) gives following results:
dnslookup captiveportal.kuketz.de https://one.one.one.one/dns-query
dnslookup master
Server: https://one.one.one.one/dns-query
dnslookup result (elapsed 135.275716ms):
;; opcode: QUERY, status: SERVFAIL, id: 22106
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 0
;; QUESTION SECTION:
;captiveportal.kuketz.de. IN A
dnslookup captiveportal.kuketz.de https://dns.quad9.net/dns-query
dnslookup master
Server: https://dns.quad9.net/dns-query
dnslookup result (elapsed 178.113493ms):
;; opcode: QUERY, status: NOERROR, id: 14606
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0
;; QUESTION SECTION:
;captiveportal.kuketz.de. IN A
;; ANSWER SECTION:
captiveportal.kuketz.de. 43200 IN A 46.38.242.112
dnslookup captiveportal.kuketz.de https://base.dns.mullvad.net/dns-query
dnslookup master
Server: https://base.dns.mullvad.net/dns-query
dnslookup result (elapsed 298.461875ms):
;; opcode: QUERY, status: NOERROR, id: 54012
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0
;; QUESTION SECTION:
;captiveportal.kuketz.de. IN A
;; ANSWER SECTION:
captiveportal.kuketz.de. 43200 IN A 46.38.242.112
So Cloudflare doesn’t return an IP address for the query.
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I was confused at first, because private DNS was set to automatic, but yes: all wifis I tested use the same adguard DNS server upstream, which then load balanced between Quad9 and Cloudflare. I too can observe Cloudflare returning SERVFAIL.
Taking Cloudflare out of the equation made the connectivity check work and apps started behaving normally again!
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Thank you for the report and suggestion. Your comment was excellent and on point—it solved my problem. I changed the Cloudflare DNS (1.1.1.3 and 1.0.0.3) to Quad9 (primary and secondary). Now it’s connecting normally. On both routers I tested, I didn’t consider the possibility that the problem could be the Cloudflare DNS.
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Turns out I had multiple issues: one with the DNS and another one with IPv6 on the FP6: iodeOS 7.6: Broken IPv6 support on WLAN
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