Hetzner and Proxmox: Using IPv6 with Router-VM

Since my instructions for setting up a pfSense router VM have been so well received by Hetzner, I would like to explain today how you can also use the IPv6 assigned by Hetzner with this VM.


In the meantime, I have turned my back on the pfSense project and switched fully to OPNSense. The reasons for this are manifold, but first of all I like the interface of the OPNSense much better. Whether you use a pfSense or an OPNSense VM, however, should be completely irrelevant – only the menu items could be found in different places.

Hetzner assigns each dedicated server a /64-IPv6 network, which can be freely routed to its MAC addresses. For this you have to click on the small computer behind the IPv6 subnet in the robot. Here we change the routing to the MAC address of the router VM.

Configuration WAN interface

The configuration of the WAN interface is very simple, so I just want to show a screenshot:

As you can see we are using DHCP6 here and have the IP address for the WAN assigned to us by Hetzner. I needed to restart the VM after enabling IPv6 on the WAN. In the dashboard you can see the newly assigned IPv6 addresses on the WAN interface – in my case this was the fe80::250:56ff:fe00:222c.

The DHCPv6 client configuration (Request only to IPv6 prefix, Send IPv6 prefix hint and Use IPv4 connectivity) has to be set – without these options I had no success.

LAN Interface Configuration

Also here I would like to use a screenshot to show the configuration.

Configuration of the LAN interface für IPv6

For the IPv6 address, it is best to use the first IPv6 address from the subnet assigned by Hetzner (at my site: 2a01:4f9:2a:129e:: 64). Further settings are not necessary here!

Gateway configuration

Unfortunately, the OPNSense didn’t always reach me via IPv6, so I puzzled for some time what was going on.

Under System -> Gateways the error was hidden. Here I have adapted the gateway accordingly:

Configuration of the Gateway für IPv6

I didn’t set the gateway as default gateway and I entered the static IPv6 address instead of leaving the gateway on „dynamic“ – but the real problem resulted from the missing default gateway.

After finishing the work I restarted the OPNSense and tested the IPv6 availability again: with success.

Configuration of a VM

Finally, I would like to show you how to make a Ubuntu or Windows VM accessible via IPv6 in this setup. I have decided against the use of DHCP6 in the internal network and configure the virtual machines statically.

The configuration of a Ubuntu-/Debian-VM is usual easy to manage. For this we add our IPv6 configuration block to the file /etc/network/interfaces:

iface ens18 inet6 static
    address 2a01:4f9:2a:129e::2 # freely selectable IPv6 address
    netmask 64
    gateway 2a01:4f9:2a:129e::1 # IPv6 address of pfSense/OPNSense

Pretty simple, isn’t it?

Configuration Windows

The configuration of the Windows VM is also quite simple for once. Enable IPv6 in the adapter settings, if this has not already been done, and enter the same data there as under Linux:

  • Address: freely selectable IPv6 address from the subnet
  • Subnet Mask: /64
  • Gateway: IPv6 address of pfSense/OPNSense

In both configurations you may have to enter one or more IPv6 name servers in order for the name resolution to work properly.

Bottom line

On the internet you can read many horror stories about the configuration of IPv6 at Hetzner – but if you are occupied with the whole setup the setup isn’t difficult at all in the end and done pretty quickly.

I will be happy to answer any questions or to receive information about my setup. It’s certainly not perfect, I know that, but it works reliably for me, which is why I actually think about it. I’m very happy. If somebody has a good tip for you: please feel free to add it to your comments!

Hetzner and Proxmox: pfSense as Gateway

As many of my readers know, I use some Hetzner servers in combination with the virtualization solution Proxmox.

To make the setup a little more secure and not rely on the Hetzner firewall, I recently took care of shielding my virtual machines behind a pfSense VM. The network configuration was not quite trivial and therefore I would like to give my readers a little insight.


  • dedicated Hetzner server (here: EX41-SSD)
  • running Proxmox system
  • an additional IP for the pfSense VM with MAC address (Hetzner-Robot)
  • Subnet, routed to the pfSense VM

As soon as these requirements are met, we can start configuring the system.

Proxmox Configuration

My Proxmox configuration looks like this (/etc/network/interfaces):

auto lo
iface lo inet loopback

iface eth0 inet manual

auto vmbr0
iface vmbr0 inet static
        address  <SERVER-HAUPT-IP>
        gateway  <SERVER-HAUPT-GATEWAY>
        pointopoint <SERVER-HAUPT-GATEWAY>
        bridge_ports eth0
        bridge_stp off
        bridge_fd 0

        up ip route add via dev vmbr0
        up ip route add via dev vmbr0
        up ip route add via dev vmbr0

        up sysctl -w net.ipv4.ip_forward=1
        up sysctl -w net.ipv4.conf.eth0.send_redirects=0

# Virtual switch for DMZ
# (connect your firewall/router KVM instance and private DMZ hosts here)
auto vmbr1
iface vmbr1 inet manual
        bridge_ports none
        bridge_stp off
        bridge_fd 0

You can read the main server IP and the main server gateway from the Hetzner Robot – there are actually not many sources of error here.

pfSense Configuration

WAN/LAN configuration

The pfSense configuration is not really more complicated. In the Proxmox interface we create the VM with two network devices, one bound to vmbr0 – our WAN interface – and one to vmbr1 – the LAN interface.

After the pfSense installation, we assign the interfaces in pfSense accordingly and configure the WAN interface:

pfSense WAN Configuration

The configuration of the LAN interface should be self-explanatory – private subnet, no gateway.

Virtual IP Address

To be able to use our subnet behind pfSense, we now have to enter each IP to be used under „Firewall -> Virtual IPs“. Here it is possible to enter all IP addresses of the subnet, we do not need a broadcast or host address.

Internal IP addresses

We are now able to distribute their IP addresses to our clients in the LAN. Either you use the DHCP server of pfSense and assign static reservations in the simplest case or you configure the clients manually.

I decided to use the DHCP variant, but I don’t want to go into the configuration here, because it’s quite self-explanatory.

1:1 NAT

In order to be able to reach our internal clients now also from the Internet, we still have to configure the 1:1 NAT.

1:1 NAT configuration

Firewall configuration

Finally, it is up to the administrator to configure the firewall correctly. There are so many solutions here, I don’t want to go into them any further. which ports are opened where, the operator of the firewall has to decide for himself.

ICMP ping rule

I find it quite pleasant to be able to check the accessibility of a host from the outside with a ping. I always create this rule in the pfSense firewall first:

pfSense ICMP Ping Rule

The internal IP or the internal subnet must of course be specified as the destination.

Bottom line

The configuration of a pfSense VM at Hetzner is not quite trivial, but it can be easily done. A little Trial & Error is included, but that’s always the case with firewalls. As a little tip I would like to give you not to block the access to the Proxmox web interface too early, so that in case of doubt you still have access to the pfSense console when you configure yourself.

I will be happy to answer any questions or to receive information about my setup. It’s certainly not perfect, I know that, but it works reliably for me, which is why I’m actually quite happy about it. If somebody has a good tip for you: please feel free to add it to your comments!

IPv6 configuration

The IPv6 configuration I have a own article.

Hetzner & Proxmox: Network Configuration


As already known, I use a Proxmox setup on servers of the German host Hetzner for myself and my customers. The wiki article about the Proxmox configuration is unfortunately not really up-to-date or easy to understand…

Often my readers asked me to pour the basic network configuration into an article: said, done – here’s the article!


In principle, you don’t have to prepare much to use a simple Proxmox setup.

Of course we need a dedicated server with installed Proxmox image and an additional IP from the Hetzner robot. We assume the following IP addresses:

  • dedicated main IP
    • IP:
    • Gateway:
  • Additional IPs (ordered via Robot – without MAC address!)

We also enable IP forwarding by executing the following command:

sysctl -w net.ipv4.ip_forward=1

We permanently enable forwarding by inserting the corresponding line in /etc/sysctl.d/99-hetzner.conf or removing the comment character.

More preparation is not necessary in this case.

Configuration Proxmox Host

On the Proxmox host, the /etc/network/interfaces file looks like this:

auto eth0
iface eth0 inet static
auto vmbr0
iface vmbr0 inet static
	bridge_ports none
	bridge_stp off
	bridge_fd 0
	bridge_maxwait 0
		up ip route add dev vmbr0
		up ip route add dev vmbr0
		up ip route add dev vmbr0
		up ip route add dev vmbr0

It is important here to enter the main IP (here: for the eth0 and vmbr0 devices as a quasi „double“ entry. The gateway address must also be entered at gateway and pointopoint – Attention: pointopoint has only one t in the middle, this is not a typo!

A reboot later should display two network devices – eth0 and vmbr0.

Virtual Machine Configuration (Linux)

After the installation I change the file /etc/network/interfaces as follows:

auto eth0
iface eth0 inet static

After a restart the VM should be reachable via ping as well as via SSH.

Virtual Machine Configuration (Windows)

Sometimes you also need a Windows machine, which is why I would like to show the configuration here simply by screenshot:

he DNS servers can of course be customized, but the rest should look the same – with your own IP addresses, of course.

The option „Check settings on exit“ must not be activated, since Windows – just like Debian – checks the configuration and would report an error – despite these error messages of the The virtual machines are running completely stable.

Bottom line

The configuration is actually quite simple and very clear. By adding a single line in the network configuration, additional IP addresses can be added and superfluous ones removed. The configuration runs very stable, you don’t have to bother with DHCP servers and the performance is also satisfactory.

I hope I have been able to help some readers – and of course Google visitors – with my instructions and of course I am happy to support you in setting up your own setup – just contact me for a non-binding offer!

Questions, criticism and hints to the article I accept naturally gladly in the comments – please have however also understanding that I can offer free support only in certain framework.

Debian Buster: SSH „Connection refused“

Nach einer Neuinstallation oder dem Upgrade auf Debian Buster konnte ich mich nicht mehr per SSH an meinem Server anmelden. Mich begrüßte ständig nur die Meldung Connection refused.

Interessanterweise konnte ich das Problem immer „lösen“, indem ich mich per Konsole direkt an der Maschine angemeldet hatte (geht dank Proxmox ja ganz einfach). Nach nur einem Login funktionierte die SSH-Verbindung wieder problemlos.

Nach einiger Recherche bin ich dann auf diesen Bug gestoßen. Um es kurz zu machen benötigt die Generierung von zufälliger Entropie mehr Zeit als zuvor unter Debian Stretch – der Start des OpenSSH-Servers benötigt allerdings ebendiese Entropie und dauert daher sehr viel länger als zuvor.

Eine einfache Lösung des Problems ist die Installation des Pakets haveged. Direkt nach der Installation dieses Pakets und einem erneuten Neustart ist das Problem behoben.

Was ist haveged? Kurz umrissen haben es die Kollegen des Linux Magazin:

Das Verfahren macht sich den Umstand zunutze, dass moderne Prozessoren Elemente zur Verzweigungsvorhersage (Branch Prediction), Caches, Pipelines und vieles mehr besitzen. Das normale Benutzen der CPU löst ein Trommelfeuer an Statusänderungen bei Tausenden dieser Elemente aus, und genau daraus produziert das Havege-Verfahren viel und hochwertigen Zufall.

Linux Magazin

Das erklärt auch, wieso der Start nun sehr viel schneller von statten geht. Vielleicht hilft es ja dem ein oder anderen verzweifelten Buster-User…

Proxmox: ungenutzte Kernel entfernen

Heute nur ein Kurztipp zum Sonntag!

Jeder Admin kennt das: man nutzt seinen Proxmox-Server schon ein paar Monate und es sammeln sich immer mehr ungenutzte Kernelversionen an… möchte man diese nun entfernen, kann man das natürlich händisch mit dpkg, apt oder aptitude machen – einfacher ist es aber mit pvekclean!

pvekclean ist ein kleines Skript von Jordan Hillis, das man gratis bei Github bekommt. Die Installation ist sehr simpel:

git clone https://github.com/jordanhillis/pvekclean.git
cd pvekclean
chmod +x pvekclean.sh


Beim ersten Start fragt das Skript, ob es sich zum einfacheren Aufruf in den Ordner /usr/local/sbin kopieren darf; kann man halten wie man möchte, ich finde es ganz angenehm. Hat man die Nachfrage bestätigt, kann man das Script ganz einfach via


aufrufen. Die Ausgabe bei mir sah so aus:

█▀▀█ ▀█ █▀ █▀▀   █ █ █▀▀ █▀▀█ █▀▀▄ █▀▀ █
█  █  █▄█  █▀▀   █▀▄ █▀▀ █▄▄▀ █  █ █▀▀ █
█▀▀▀   ▀   ▀▀▀   ▀ ▀ ▀▀▀ ▀ ▀▀ ▀  ▀ ▀▀▀ ▀▀▀

█▀▀ █   █▀▀ █▀▀█ █▀▀▄ █▀▀ █▀▀█
█   █   █▀▀ █▄▄█ █  █ █▀▀ █▄▄▀   ⎦˚◡˚⎣ v1.2
▀▀▀ ▀▀▀ ▀▀▀ ▀  ▀ ▀  ▀ ▀▀▀ ▀ ▀▀
By Jordan Hillis [contact@jordanhillis.com]

Usage: pvekclean [OPTION]

  -f,   --force         Remove all old PVE kernels without confirm prompts
  -s    --scheduler     Have old PVE kernels removed on a scheduled basis
  -v,   --version       Shows current version of pvekclean
  -r    --remove        Uninstall pvekclean from the system

OS: Debian GNU/Linux 9 (stretch)
Boot Disk: 74% full [342M/488M used, 121M free]
Current Kernel: pve-kernel-4.15.18-16-pve

[*] Boot disk space used is healthy at 74% capacity (121M free)
[-] Searching for old PVE kernels on your system...
[*] "pve-kernel-4.15.18-10-pve" has been added to the kernel remove list
[*] "pve-kernel-4.15.18-11-pve" has been added to the kernel remove list
[*] "pve-kernel-4.15.18-12-pve" has been added to the kernel remove list
[*] "pve-kernel-4.15.18-13-pve" has been added to the kernel remove list
[*] "pve-kernel-4.15.18-14-pve" has been added to the kernel remove list
[*] "pve-kernel-4.15.18-15-pve" has been added to the kernel remove list
[-] PVE kernel search complete!
[!] Would you like to remove the 6 selected PVE kernels listed above? [y/N]: Y
[*] Removing 6 old PVE kernels...DONE!
[*] Updating GRUB...DONE!
[-] Have a nice day ⎦˚◡˚⎣

Natürlich sollte man, bevor man die Abfrage zum endgültigen Löschen bestätigt, sicher sein, dass der aktuelle Kernel nicht entfernt wird. Führt man das Skript nun in regelmäßigen Abständen aus, bleibt die Kernelliste auf dem Server immer schön sauber!