add basic ipv6 article for standard DSL (#29)

source/manual/how-tos/ipv6_dsl.rst

@@ -0,0 +1,50 @@
+=====================================
+Configure IPv6 for generic DSL dialup
+=====================================
+
+------------
+Introduction
+------------
+
+This short article shows how to setup IPv6 on a standard DSL connection and how
+to handover the delegated prefix from your provider in your local LAN.
+
+It's compatible and tested for but not limited to:
+
+- Deutsche Telekom
+
+-------------------------
+Step 1 - General Settings
+-------------------------
+
+Go to **System->Settings->General->** and check that **Prefer IPv4 over IPv6** 
+is not ticked. This value is default so just check if it has been touched.
+
+Also enable **Allow DNS server list to be overridden by DHCP/PPP on WAN** at the 
+bottom, so you get the correct DNS servers if you just use IPv4 ones.
+
+-------------------
+Step 2 - Allow IPv6
+-------------------
+
+Next go to **Firewall->Settings->Advanced** and verfiy that **Allow IPv6** is enabled.
+
+--------------------------------
+Step 3 - Interface Configuration
+--------------------------------
+
+In **Interfaces->WAN** and set **IPv6 Configuration Type** to DHCPv6 and in section
+**DHCPv6 client configuration** at the bottom tick:
+
+- Request only an IPv6 prefix
+- Send IPv6 prefix hint
+- Use IPv4 connectivity
+
+Set the prefix size to the one your provider delegates, mostly /56 or 64, sometimes /48.
+
+Then change to **Interfaces->LAN** and set **IPv6 Configuration Type** to **Track Interface**.
+At the bottom in section **Track IPv6 Interface** choose **IPv6 Interface** as WAN and for
+**IPv6 Prefix ID** a value of 0 is perfectly fine.
+
+Hit Apply and disable/enable the NICs of your internal systems. Depending on the system
+and vendor, also a reboot could be required.

source/manual/ipv6.rst

@@ -23,3 +23,4 @@ Configuring
 
 - :doc:`/manual/how-tos/IPv6_ZenUK`
 - :doc:`/manual/how-tos/ipv6_tunnelbroker`
+- :doc:`/manual/how-tos/ipv6_dsl`