Mal <malz@jetlan.com> writes:

On Debian 6.1.129-1, I have a static network interface conf (no Netplan)
with both IPv4 & IPv6 addressing and Name-servers set.

[...]

On another older machine (running kernel 4.9.35-v7+) with exactly the
same configuration layout, I get BOTH the IPv4 & IPv6 addresses returned
from resolv.conf

Unfortunately, I am unsure what the issue is. However, I would like to
point out that Debian version numbers differ from the kernel version,
which is merely one component of the system. Please refer to /etc/debian_version and /etc/os-release to determine the version of the distribution you are running.

The current kernel version for Debian 12, codename "bookworm", is
6.1.129-1. The 4.9 kernel was in Debian 9 "stretch", which is quite
outdated, and many relevant components have been updated since, so even
with "exactly the same configuration layout", you can expect different behaviour.

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Hello,

first of all the nameservers in /etc/resolv.conf are queried in order.
That means the 2'nd one is only queried when the first one does not
answer. Even NXDOMAIN is a valid answer.
So the first one should also return IPv6 over a IPv4 connection.

How do you query the nameserver? dig, 'getent hosts' ... ?


Am 27.03.25 um 05:04 schrieb Mal:

Hello

On Debian 6.1.129-1, I have a static network interface conf (no Netplan)
with both IPv4 & IPv6 addressing and Name-servers set.

root@debian:/home/user# more /etc/network/interfaces
source /etc/network/interfaces.d/*
# The loopback network interface
 auto lo
 iface lo inet loopback

 allow-hotplug enp1s0
 iface enp1s0 inet static
 address 12.34.56.78
 network 12.34.56.0
 netmask 255.255.255.0
 broadcast 12.34.56.255
 gateway 12.34.56.1

 iface enp1s0 inet6 static
 address 2xxx:xxxx:x00:1::50
 netmask 64
 gateway 2xxx:xxxx:x00:1::1
 dns-nameservers 12.34.56.80  2xxx:xxx:x00:1::80

When I query what is set in resolv.conf file, It only returns the IPv4 host.

root@debian:/home/user# more /etc/resolv.conf
nameserver 12.34.56.80

On another older machine (running kernel 4.9.35-v7+) with exactly the
same configuration layout, I get BOTH the IPv4 & IPv6 addresses returned
from resolv.conf

root@another:/home/user# more /etc/resolv.conf
nameserver 12.34.56.80
nameserver 2xxx:xxx:x00:1::80

The IPv6 networking side has no issues - I can ssh over to other
machines via IPv6 with no issues.  And the machine is serving v6 web
traffic fine.

Mal

--- SoupGate-Win32 v1.05
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Hi,

On Thu, Mar 27, 2025 at 02:34:13PM +1030, Mal wrote:

On Debian 6.1.129-1, I have a static network interface conf (no Netplan)
with both IPv4 & IPv6 addressing and Name-servers set.

I don't know why only your IPv4 address is making it into resolv.conf,
but if the network setup is static then I would (and do) just put both
into resolv.conf manually rather than use resolvconf package - this is
what the dns-nameservers configuration is talking to.

If you want to debug it further, resolvconf will install something in /etc/network/interfaces.d which looks for these dns-nameservers settings
in order to update the file, so have a look what they do.

Thanks,
Andy

--
https://bitfolk.com/ -- No-nonsense VPS hosting

--- SoupGate-Win32 v1.05
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On Thu, Mar 27, 2025 at 14:34:13 +1030, Mal wrote:

root@debian:/home/user# more /etc/network/interfaces
source /etc/network/interfaces.d/*
# The loopback network interface
 auto lo
 iface lo inet loopback

 allow-hotplug enp1s0
 iface enp1s0 inet static
 address 12.34.56.78
 network 12.34.56.0
 netmask 255.255.255.0
 broadcast 12.34.56.255
 gateway 12.34.56.1

 iface enp1s0 inet6 static
 address 2xxx:xxxx:x00:1::50
 netmask 64
 gateway 2xxx:xxxx:x00:1::1
 dns-nameservers 12.34.56.80  2xxx:xxx:x00:1::80

That dns-nameservers line is only used if you're running the "resolvconf" package.

When I query what is set in resolv.conf file, It only returns the IPv4 host.

root@debian:/home/user# more /etc/resolv.conf
nameserver 12.34.56.80

I would look at the timestamp on that file. Is it being updated at all?

Next, I would verify that you've installed the resolvconf package, since
your configuration is relying on it. Or, as another person suggested
already, skip the resolvconf package entirely, and just use a static resolv.conf file.

--- SoupGate-Win32 v1.05
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On Thu, Mar 27, 2025 at 21:38:02 +1030, Mal wrote:

Without the conf package, I still don't get why it populated only one
ipv4 nameserver target and ignored the ipv6 target.

You're making an assumption. All you actually know is what was in the
file; you don't know HOW it got there. (Or when.)

The contents of that file might have been generated at any time in
the past, by anyone or anything.

--- SoupGate-Win32 v1.05
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Hi,

On Thu, Mar 27, 2025 at 09:38:02PM +1030, Mal wrote:

Without the conf package, I still don't get why it populated only one
ipv4 nameserver target and ignored the ipv6 target.

Are you sure this is not just what the installation process did?

Without "resolvconf" the /etc/resolv.conf file is just a static file so
there's limited things that would be editing it. The guesses of "you"
or "the installer" would be the most likely for me as nothing else
should be touching it.

Thanks,
Andy

--
https://bitfolk.com/ -- No-nonsense VPS hosting

--- SoupGate-Win32 v1.05
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On Thu, Mar 27, 2025 at 13:06:54 +0000, Andy Smith wrote:

Hi,

On Thu, Mar 27, 2025 at 09:38:02PM +1030, Mal wrote:

Without the conf package, I still don't get why it populated only one
ipv4 nameserver target and ignored the ipv6 target.

Are you sure this is not just what the installation process did?

Without "resolvconf" the /etc/resolv.conf file is just a static file so there's limited things that would be editing it. The guesses of "you"
or "the installer" would be the most likely for me as nothing else
should be touching it.

The most common program that writes to resolv.conf is a DHCP client
daemon (any of them). If the system was originally installed with
DHCP, and then later changed to static addressing, the resolv.conf
file might have been written by whichever dhcpcd was installed at
the time, and then never modified again once the transition to static addressing was made.

Whoever or whatever wrote the file is irrelevant now, though.

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