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Intermittend IPv6 connection failures

Jung-Fernmelder 0 Reputation points
2025-12-13T19:45:25.3766667+00:00

Dear Microsoft community,

on a machine running Windows 11 Pro 24H2 were IPv6 connections unavailable intermittendly. The browser connected via IPv4 with every website; pings failed when IPv6 was enforced. Typically this behaviour started about five minutes after plugging in the network cable and remained until plugging in and out the network cable.

Carrier: Vodafone 5G Router: ZTE MU5002 Browser: Mozilla Firefox 146.0 Location: Germany Local user account without admin rights Build: 26100.7462

The solution was resetting the firewall rules to default via Windows Defender Firewall with advanced security. And the network was set as a private network.

I think, there were no changes applied to the firewall rules manually. I don't know whether third party software applied changes to the firewall rules (there is some software installed which may do so, i.e. Wireshark, RustDesk, TeamViewer, WinSCP). The issue is gone for five days and didn't reappear so far (and I hope it won't reappear anymore).

This experience report might help people who face unavailability of IPv6 connections intermittendly.

Best regards

(PII removed)

Attachment: 4 screenshotsScreenshot 1

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Windows for home | Windows 11 | Internet and connectivity
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  1. Thomas4-N 5,415 Reputation points Microsoft External Staff Moderator
    2025-12-15T10:12:15.4133333+00:00

    (Please note that our forum is a public platform, and we will modify your question to hide your personal information in the description. Kindly ensure that you hide any personal or organizational information the next time you post an error or other details to protect personal data.)

    Hello Jung-Fernmelder, welcome to Microsoft Q&A forum.

    Thank you for sharing your finding — I appreciate the effort you put into troubleshooting and documenting the outcome. This will definitely help others who run into similar symptoms.

    If the behavior shows up again or seems unusual, you may also want to report it through the Windows Feedback Hub app or the Microsoft Feedback Portal website, so the product teams can take a closer look.

    Thanks again for contributing to the forum!

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  2. Jung-Fernmelder 0 Reputation points
    2025-12-16T05:28:09.9266667+00:00

    You're welcome.

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