System and Network configuration • Unwanted Secondary IPv6 Address Blocking Internet Access

Hi,

I have a Debian 12 server connected to my router via LAN.

After booting, I can ping external IPv6 addresses, a few minutes later I cannot. It turns out that my server "receives" a second IPv6 address, which is not known and therefore not routed by my router. Unfortunately, my server uses this second address to send packets, which means there is no return path from the internet, and thus all external connections fail.
Incoming connections and outgoing LAN connection do work.

If I manually delete the unwanted address, everything works as it should - until it comes back after 2-3 minutes!

I have checked syslog, but there is nothing regarding this. The server seems to create the second address all by itself, using the prefix my router gave it.
The interface is configured in /etc/network/interfaces as follows:Being desperate, I have also tried dhcp, which my router does not provide on ipv6, and static, both to no avail. I did not really expect this to help anyway ...

Has anyone seen this behavior and knows how to solve it?

Statistics: Posted by Kian — 2024-10-11 08:06

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