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iOS 26 / 26.0.1 - No or slow DNS on cellular

Hello,

after I installed iOS 26 on my iPhone 14 Pro, DNS requests for installed NextDNS app in mobile became extremely slow or broke off with timeout. Uninstalling of the app and setting up a NextDNS profile also did not solve the problem.
There were no problems in the WLAN.
Also, a reset of the network settings and a restart of the mobile phone did not bring a solution.

Even after switching to an iPhone 17 Pro, the problem was reproducible. With other DNS profiles, e.g. Mullvad, it works without problems.
Even use without private relay has not brought any improvement.
iOS 26.0.1 also not.

I tested all this in the network of Deutsche Telekom and Vodafone. To my knowledge, both networks rely entirely on IPv6.
My landline is also natively IPv6, but the problem does not occur in the WLAN via it.

The issue does not occur on an iPhone 13 Pro with iOS 18.x.

Is anything known that Apple has changed anything in the current versions that can trigger this behavior? And if so, how can I solve the problem?

Greeting
Wutti

5 replies

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    • wutti
    • 2 wk ago
    • Reported - view

    Ok, if I try the check on ping.nextdns.io without any profile in cellular network of Telekom Germany, there are only errors.

    So option 1, Telekom and Vodafone blocks NextDNS, option 2 Apple blocks NextDNS. But with activated Private Relay, there are the errors in the check. Without Private Relay there is a blank site on ping.nextdns.io.
     

    I‘m very confused

    • wutti
    • 2 wk ago
    • Reported - view

    ok, I found the error. Using the standard APN settings for Deutsche Telekom mobile on iPhone with iOS26 uses IPv6 only.

    After switching the APN settings to IPv4, DNS over NextDNS works without problems.

    But... This is only a workaround. IPv4 is not a solution. So NextDNS should check why IPv6 isn't working and fix this problem.

    • wutti
    • 2 wk ago
    • Reported - view

    But it‘s curious that the IPv6 connection problem is not available on landline. Only on cellular. 

    • wutti
    • 10 days ago
    • Reported - view

    No one else with this problem? And no idea from the developers?

    • wutti
    • 9 days ago
    • Reported - view

    Ok, next new information. Activated Private Relay with generic location instead of country and timezone and APN internet.v6.telekom works.

    Spooky

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