IPv6 allocation problem on Debian 11

OS type and version Debian 11 (Bullseye)
Virtualmin version 7.1-1

Hi guys,

I’m trying the new Virtualmin 7.0 Beta on a Debian 11 Server. So far everything is running actually great. I just found out, at least on my system, when I do a reboot, all my IPv6 addresses of the servers are not going to allocate automatically to my eth0 device.
Going to Webmin → Network Configuration → Network Interfaces, I can see these IPs allocated to the eth0 device in the “Activated at Boot” tab. Switching to active now, those are not all allocated, just the default ::1 IP.
Switching back to the “Activated at Boot” tab, going to the eth0 settings, and just click on “Save and Apply” all IPv6 IPs are getting allocated to eth0.
I don’t know at the moment where to look for to get this issue fixed :slight_smile:
Maybe anyone from here can help out?

Thanks already a lot upfront.


As you go to Networking ⇾ Network Configuration: Edit Bootup Interface page is Activate at boot? option set to Yes?

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Hi Ilia,

yes, it’s activated. At least it says under Active “yes”

The strange part is that under the “Routing and Gateway” tab, those IPs aren’t visible on the active connection tab.

I would assume that if you configured static IPv4 and IPv6 addresses for the interface, and had it activated at boot, it would work as expected:

Please make sure to have a backup of /etc/network/interfaces file before making this change and that your server is accessible via a console.

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Hi Ilia,

thanks a lot for your answer.
Yes, everything is actually configured like in your Screenshot.

I was looking as well these days in my interface’s config file, but I haven’t found any errors in it.
It looks like more or less the same as on my Debian 10 production server.

# The loopback network interface
auto 0 lo conf eth0
iface lo inet loopback

# The primary network interface
iface eth0 inet static
        address 123.456.134.122
        network 123.456.128.0
        gateway 123.456.128.1
        up ip route replace 123.456.128.0/19 via 123.456.128.1 dev eth0

iface eth0 inet6 static
        pre-up /sbin/modprobe -q ipv6 ; /bin/true
        address 1234:5678:1234:8207:0000:0000:0000:0001
        netmask 64
        up ifconfig eth0 inet6 add 1234:5678:1234:8207::100/64
        up ifconfig eth0 inet6 add 1234:5678:1234:8207::101/64
        up ifconfig eth0 inet6 add 1234:5678:1234:8207::102/64
        gateway fe80::1

Not sure if maybe the IPv6 short addresses(1234::100) make these problems. I’ll try to change it now and make a test again. → No, no change. I’ll try to reinstall the server, something is not working properly there I think. I think it’s not even a Virtualmin “error”.

Just found the solution.

Thanks a lot @Ilia for guiding me into the right direction. And I understand now more about this file.

First, looking at my interface config file, the first line

auto 0 lo conf eth0

looks a bit weird.

I don’t have any interface which is named 0 or conf, so I changed it to

auto lo eth0

Second of all, it looks like on Debian 11 there is no “ifconfig” installed out of the box.
So I installed the net-tools, did a restart of the whole server and now everything works like a charm without any problems.

P.S.: the “conf” and “0” interface gets assigned to the file on the first creation of a server in Virtualmin. Not sure, if this is correct or a bug…

Again, thanks a lot @Ilia, it looks like the RC-13 of VM7 works pretty well on Debian 11 now. I have faced some issues with fail2ban as well, but I could fix them without problems.

1 Like

You’re welcome.

I don’t have any interface which is named 0 or conf, so I changed it to

Can you remember what changes you made using Virtualmin/Webmin UI. We would like to reproduce the issue.

That looks concerning. @Jamie Do you know if Webmin could by accident add 0 to that auto 0 lo conf eth0 line?

I can’t see how that would happen - Webmin only ever adds interface names to auto , but will preserve all names that are already there.

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