diff --git a/docs/routing/create-dummy-interface.md b/docs/routing/create-dummy-interface.md
new file mode 100644
index 0000000..cd811df
--- /dev/null
+++ b/docs/routing/create-dummy-interface.md
@@ -0,0 +1,43 @@
+
+# Create a dummy interface
+
+For routes to be installed into the kernel, the source IP must be bound to an interface. Often the CRXN address is not on any interface. Therefore one creates a dummy interface. Alternatively, you can bind the CRXN IP address to the loopback interface. If the CRXN IP address is not bound to an interface, the `Netlink: Invalid argument` error can occur at bird.
+
+You can create a dummy interface with the following command:
+```
+ip link add crxn type dummy
+ip link set dev crxn up
+```
+Here `crxn` is the name of the interface.
+
+To bind the CRXN IP address to the interface you can use the following command:
+```
+ip addr add dev crxn <ip>/128
+```
+Replace `<ip>` with the CRXN IP address.
+
+To delete the dummy interface you can use the following command:
+```
+ip link del crxn
+```
+
+## Automatic start with ifupdown
+
+```
+auto crxn
+iface crxn inet6 manual
+    pre-up ip link add crxn type dummy
+    up ip addr add dev crxn <ip>/128
+    post-down ip link del crxn
+```
+
+Alternatively, you can use the following configuration:
+```
+auto crxn
+iface crxn inet6 static
+	address <ip>
+	netmask 128
+    pre-up ip link add crxn type dummy
+    post-down ip link del crxn
+```
+Here the assignment of the IP address is delegated to ifupdown.
diff --git a/docs/routing/index.md b/docs/routing/index.md
index 609d418..7c26bf9 100644
--- a/docs/routing/index.md
+++ b/docs/routing/index.md
@@ -3,3 +3,4 @@
 
 - [Forwarding](forwarding)
 - [Setting up Bird](bird)
+- [Create a dummy interface](create-dummy-interface)
diff --git a/docs/tunneling/index.md b/docs/tunneling/index.md
index 2b48962..7243490 100644
--- a/docs/tunneling/index.md
+++ b/docs/tunneling/index.md
@@ -3,4 +3,5 @@
 
 - [fastd](fastd)
 - [WireGuard](wireguard)
+- [OpenVPN](openvpn)
 - [IP tunnel](iptunnel)
diff --git a/docs/tunneling/openvpn.md b/docs/tunneling/openvpn.md
new file mode 100644
index 0000000..be1a0ec
--- /dev/null
+++ b/docs/tunneling/openvpn.md
@@ -0,0 +1,59 @@
+
+# OpenVPN
+
+**Hint:** OpenVPN with a static key has no Perfect Forward Secrecy (PFS)!
+
+## Configuration
+
+```
+mode p2p
+
+remote <remote>
+local <local>
+
+proto <proto>
+
+rport <rport>
+lport <lport>
+
+dev-type tun
+dev <interface>
+
+script-security 1
+cipher aes-256-cbc
+
+resolv-retry infinite
+
+persist-key
+persist-tun
+
+ifconfig-ipv6 <IPv6> fe80::1000
+
+secret <secret>
+```
+Replace `<remote>` with the IP address of the peer and `<local>` with your IP address.
+Replace `<proto>` with `udp` for a connection over IPv4 or with `udp6` for a connection over IPv6.
+Choose a port for `<lport>` and set `<rport>` to the port of your peer. `<lport>` on udp must be opened accordingly in the local firewall.
+Replace `<interface>` with the appropriate interface name for your peer.
+Replace `<IPv6>` with your link-local IPv6. The specification of a second link-local address is only necessary for certain functions of OpenVPN, but the specification is mandatory. Therefore the address `fe80::1000` is used here.
+Replace `<secret>` with the path to the Secret Static Key.
+
+Generate a Secret Static Key:
+```
+openvpn --genkey secret <filename>.key
+```
+
+## Automatic start with systemd
+
+If you save the OpenVPN configuration under `/etc/openvpn/<filename>.conf`, you can use systemd to start the OpenVPN connection or set an automatic start:
+```
+systemctl start openvpn@<filename>
+```
+```
+systemctl enable openvpn@<filename>
+```
+
+## Further links
+
+- [Reference manual for OpenVPN 2.6](https://openvpn.net/community-resources/reference-manual-for-openvpn-2-6/)
+- [dn42 OpenVPN Guide](https://dn42.dev/howto/openvpn)