* An existing and functional OpenVPN configuration (use the official howto if you don't yet have this.)

* **Recommended** A routed IPv6 network block that will reach the host configured as the OpenVPN server

In this document, we'll assume you have the following from the OpenVPN server's viewpoint:

* The OpenVPN server has an IPv6 IP of 2001:db8:0:abc::100/64 on its LAN interface

There are 2 ways to add IPv6 addressing and pool options to the server, similar to what OpenVPN supports for IPv4: using a helper-directive, and by expanding the helper-directive. The expansion is required if you do not wish to use the automatic values the helper-directive supplies. Clients who use `--client` or `--pull` will get the `tun-ipv6` directive and addressing from the pool pushed as a result.

Note: the option tun-ipv6 is deprecated and not required anymore since version 2.4 (see DeprecatedOptions).

Pushing routes over the tunnel works much like it does in IPv4, but you use `--push "route-ipv6 NETWORK/CIDR"`

Otherwise, there is a way out. Typically /64 IPv6 netblocks are assigned, leaving a large address space. For an OpenVPN setup, this address space can be broken in 2, /65-prefix parts, the first being assigned to the physical network interface, and the second to the VPN. **Warning** operating netblocks smaller than /64 might break some network features.

**Avoid** this setup if you are using any of:

* SLAAC. If you are using SLAAC and have no way around, ask your ISP for permission to use static address assignment on your VPN server.

See this [Internet Draft](http://tools.ietf.org/html/draft-carpenter-6man-why64-00) for details.

You can do this also if your assigned IPv6 netblock is already shorter than /64, e.g. /112 . Just perform the same steps and compute the base address of the upper subnet: the lower starts with the last bit in the netmask set to 0, the upper starts with it set to 1.

After setting up the OpenVPN connection you are able to ping6 the Android 4.4.x device from your server, but you cannot ping6 the server or other IPv6 targets from your Android 4.4 device. This bug doesn't occur in Android 4.3 (And earlier?) and occurs in all Android 4.4.x versions including 4.4.2. There is no known workaround for this issue except hoping on a fix in Android 4.4.3.

* [Issue 63349: IPv6Droid does not work on Android 4.4 / 4.4.1](https://code.google.com/p/android/issues/detail?id=63349)

**iOS 9** broke redirect-gateway if used with IPv6 tunnels and no IPv4 traffic goes inside the tunnel. To workaround this issue, use:

combined with usual redirect-gateway. This option works only on Android and iOS OpenVPN Connect clients (OpenVPN 3) and OpenVPN 2.4 (development version) and has no effect for OpenVPN 2.3.

* [#614 Connect on iOS 9: IPv4 routing doesn't work with dual-stack](http://community.openvpn.net/openvpn/ticket/614)