Only one of IPv4 and IPv6 work in LXC container

mousi

New Member
Jan 15, 2026
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Hello, I am new to proxmox VE and I have recently installed v9.1.1.

I have an LXC container that I configured with both an IPv4 (DHCP) and IPv6 (tried both static and SLAAC). I was trying to figure out why IPv6 was not working and I figured out that only the first iface eth0 instruction in /etc/network/interfaces works!

So when I have the following only IPv4 works and I get a link local address for IPv6:
Code:
auto lo
iface lo inet loopback

auto eth0
iface eth0 inet dhcp

iface eth0 inet6 static
        address xxxx:xxxx:xxxx:xxxx::dce1/128
        gateway fe80::beee:7bff:fe6f:9f38

When I switch them around like this, IPv6 works as expected with a public address but the container doesn't get an IPv4:
Code:
auto lo
iface lo inet loopback

auto eth0
iface eth0 inet6 static
        address xxxx:xxxx:xxxx:xxxx::dce1/128
        gateway fe80::beee:7bff:fe6f:9f38

iface eth0 inet dhcp

Is this a bug or am I doing something wrong? I have tried configuring those from proxmox UI and directly by editing /etc/network/interfaces. Also I should mention, in the first case (when I set it to auto instead of static) if I manually run dhclient -6 I get a public IPv6 but if the container reboots it won't get it automatically.
 
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