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I have this strange bug on my Raspberry PI that my public IPv6 is not working (sometimes!). When I restart my Pi the IPv6 gets assigned and I can reach my Pi from the internet. However and some point it does not work anymore. If I look at ifconfig I still can see that my interface has the IPv6 assigned. However when I'm executing a curl request to an online service to get back my IPv6 I only get the IPv4 back. After a restart the same curl request will give me my IPv6.

I don't know what might cause this behavior so I have a hard time to investigating it. Any idea or help to find the issue is highly appreciated!

ifconfig:

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ping to IPv6 API:

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The command @dougie gave me fixed the issue but it would be good to know were it is coming from to prevent it in the future.

pi@home-server:~ $ curl 'https://api64.ipify.org?format=json'
{"ip":"46.87.255.134"}pi@home-server:~ $ sudo systemctl restart dhcpcd
Warning: The unit file, source configuration file or drop-ins of dhcpcd.service changed on disk. Run 'systemctl daemo                      n-reload' to reload units.
pi@home-server:~ $ systemctl daemon-reload
==== AUTHENTICATING FOR org.freedesktop.systemd1.reload-daemon ===
Authentication is required to reload the systemd state.
Authenticating as: ,,, (pi)
Password:
==== AUTHENTICATION COMPLETE ===
pi@home-server:~ $ curl 'https://api64.ipify.org?format=json'
{"ip":"2003:de:ef2b:5642:10ed:f093:609b:5c20"}pi@home-server:~ $

Edit:

I found a workaround by FP2K-Minske that solved the issue for me:

sudo nano /etc/dhcpcd.conf
denyinterfaces veth*
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    Please post cut'n'paste text not fuzzy screen captures. Have you tried sudo systemctl restart dhcpcd to solve strange networking problems.
    – Dougie
    Jan 15, 2021 at 20:59
  • Thanks @Dougie that command helped!
    – jwillmer
    Jan 16, 2021 at 9:14
  • @jwillmer This command is also executed on boot up. How long does it "fix" your problem?
    – Ingo
    Jan 16, 2021 at 16:29
  • @Dougie I can't detect a regular pattern of this issue. Sometimes it takes a day to reoccur, sometimes a week. Maybe some docker container is generating this issue. Because my server only hosts docker containers, everything else is default installation. But I don't understand how this can happen so I don't know which container could cause this.
    – jwillmer
    Jan 16, 2021 at 23:32
  • Sorry I can't help. I don't run docker.
    – Dougie
    Jan 17, 2021 at 0:30

1 Answer 1

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This actually has more to do with your router and ISP than it does the RPi. If you wish to prefer the IPv6, you can force it in a network configuration like this.

Be aware, though, that this may or may not be reliable, as not every service out there is accessible via IPv6. My ISP even had for a very long time a flaky IPv6 routing infrastructure (mostly better now for me, but not everywhere I imagine).

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  • I don't think it has to do with ISP or router. My old server with Ubuntu on it was running the same network configuration before I replaced it with the Pi and I never had problems with my IPv6. I need to use IPv6 since my server can only be reached via IPv6 from outside - my ISP shares the IPv4 with many clients.
    – jwillmer
    Jan 15, 2021 at 23:00

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