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.

Prerequisites

• 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>
        netmask  255.255.255.255
        gateway  <SERVER-HAUPT-GATEWAY>
        pointopoint <SERVER-HAUPT-GATEWAY>
        bridge_ports eth0
        bridge_stp off
        bridge_fd 0

        up ip route add 192.168.0.0/16 via 138.201.203.59 dev vmbr0
        up ip route add 172.16.0.0/12 via 138.201.203.59 dev vmbr0
        up ip route add 10.0.0.0/8 via 138.201.203.59 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:

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.

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:

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.