No options for IPv6 on guest NICs

M

matthiasnick

New Member
Jul 19, 2025
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Hello!

I'm new to the forum (as in I have never posted, just found answers so far). I could not find a situation similar to mine in the search, so I'm writing a post.

My ISP has recently enabled IPv6 for my connection. I would therefore like my Proxmox guests to get IPv6 addresses from my OPNsense router. However, no options for IPv6 even show up for the NIC in my Linux guests. As in the respective directory in /proc/sys/network/ipv6/conf does not exist.

This is my /etc/network/interfaces on the Proxmox host:

Code: 
source /etc/network/interfaces.d/*

auto lo
iface lo inet loopback

auto enp6s0f0
iface enp6s0f0 inet manual

iface enp6s0f0 inet6 manual

auto enp6s0f1
iface enp6s0f1 inet static
        address 10.0.0.4/23
        gateway 10.0.0.1

iface enp6s0f1 inet6 auto

iface eno1 inet manual

iface eno2 inet manual

iface enxd8eb97b33f04 inet manual


auto vmbr0
iface vmbr0 inet manual
        bridge-ports enp6s0f0
        bridge-stp off
        bridge-fd 0

auto vmbr1
iface vmbr1 inet static
        address 10.1.0.1/24
        bridge-ports none
        bridge-stp off
        bridge-fd 0

The NICs relating to vmbr0 are the ones not showing the IPv6 options. Any ideas as to what I'm doing wrong?

Thanks and best regards
Matthias
 
Something like:

Code: 
# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).

source /etc/network/interfaces.d/*

# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface
allow-hotplug ens18
iface ens18 inet static
        address 1.2.3.4/24
        gateway 1.2.3.1
        # dns-* options are implemented by the resolvconf package, if installed
        dns-nameservers 1.2.3.1
        dns-search example.net

iface ens18 inet6 static
        pre-down ip -6 addr flush dev ens18 scope global || :
        address aa:bb:cc:dd::4
        netmask 64
        up ip -f inet6 route add aa:bb:cc:dd::1 dev ens18
        up ip -f inet6 route add default via aa:bb:cc:dd::1 dev ens18
 
That gave me Error: ipv6: IPv6 is disabled on this device. IPv6 in general is enabled in the guest, the second interface has a Link-Local address.
 
Code: 
auto lo
iface lo inet loopback

auto eth0
iface eth0 inet dhcp

iface eth0 inet6 auto

auto eth1
iface eth1 inet static
        address 10.1.0.18/23

eth0 is the one without IPv6 options:


Code: 
   ls -la /proc/sys/net/ipv6/conf
insgesamt 0
dr-xr-xr-x 1 root root 0 20. Jul 15:12 .
dr-xr-xr-x 1 root root 0 20. Jul 15:12 ..
dr-xr-xr-x 1 root root 0 20. Jul 15:40 all
dr-xr-xr-x 1 root root 0 20. Jul 15:40 default
dr-xr-xr-x 1 root root 0 20. Jul 15:40 eth1
dr-xr-xr-x 1 root root 0 20. Jul 15:40 lo
 
Just as a follow-up, in case someone runs into the same situation: I have been successful in getting IPv6 to work by replacing dhclient with udhcpc on the guests. I do not know why this worker, but apparently it did.
 
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