examples: add wan load balancing examples

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@@ -17,3 +17,4 @@ This chapter contains various configuration Examples
    azure-vpn-dual-bgp
    tunnelbroker-ipv6
    dhcp-relay-through-gre-bridge
+   wan-load-balancing
diff --git a/docs/appendix/examples/wan-load-balancing.rst b/docs/appendix/examples/wan-load-balancing.rst
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+.. _wan-load-balancing:
+
+WAN Load Balancer examples
+==========================
+
+
+Example 1: Distributing load evenly
+-----------------------------------
+
+The setup used in this example is shown in the following diagram:
+
+.. image:: /_static/images/Wan_load_balancing1.png
+   :width: 80%
+   :align: center
+   :alt: Network Topology Diagram
+
+
+Overview
+^^^^^^^^
+ * All traffic coming in trough eth2 is balanced between eth0 and eth1
+   on the router.
+ * Pings will be sent to four targets for health testing (33.44.55.66,
+   44.55.66.77, 55.66.77.88 and 66.77.88.99).
+ * All outgoing packets are assigned the source address of the assigned
+   interface (SNAT).
+ * eth0 is set to be removed from the load balancer's interface pool
+   after 5 ping failures, eth1 will be removed after 4 ping failures.
+
+Create static routes to ping targets
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+Create static routes through the two ISPs towards the ping targets and
+commit the changes:
+
+.. code-block:: none
+
+   set protocols static route 33.44.55.66/32 next-hop 11.22.33.1
+   set protocols static route 44.55.66.77/32 next-hop 11.22.33.1 
+   set protocols static route 55.66.77.88/32 next-hop 22.33.44.1
+   set protocols static route 66.77.88.99/32 next-hop 22.33.44.1
+
+Configure the load balancer
+^^^^^^^^^^^^^^^^^^^^^^^^^^^
+Configure the WAN load balancer with the parameters described above:
+
+.. code-block:: none
+
+   set load-balancing wan interface-health eth0 failure-count 5
+   set load-balancing wan interface-health eth0 nexthop 11.22.33.1
+   set load-balancing wan interface-health eth0 test 10 type ping
+   set load-balancing wan interface-health eth0 test 10 target 33.44.55.66
+   set load-balancing wan interface-health eth0 test 20 type ping
+   set load-balancing wan interface-health eth0 test 20 target 44.55.66.77
+   set load-balancing wan interface-health eth1 failure-count 4
+   set load-balancing wan interface-health eth1 nexthop 22.33.44.1
+   set load-balancing wan interface-health eth1 test 10 type ping
+   set load-balancing wan interface-health eth1 test 10 target 55.66.77.88
+   set load-balancing wan interface-health eth1 test 20 type ping
+   set load-balancing wan interface-health eth1 test 20 target 66.77.88.99
+   set load-balancing wan rule 10 inbound-interface eth2
+   set load-balancing wan rule 10 interface eth0
+   set load-balancing wan rule 10 interface eth1
+
+Example 2: Failover based on interface weights
+----------------------------------------------
+
+This examples uses the failover mode.
+
+Overview
+^^^^^^^^
+In this example eth0 is the primary interface and eth1 is the secondary
+interface to provide simple failover functionality. If eth0 fails, eth1
+takes over.
+
+Create interface weight based configuration
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+The configuration steps are the same as in the previous example, except
+rule 10 so we keep the configuration, remove rule 10 and add a new rule
+for the failover mode:
+
+.. code-block:: none
+
+   delete load-balancing wan rule 10
+   set load-balancing wan rule 10 failover
+   set load-balancing wan rule 10 inbound-interface eth2
+   set load-balancing wan rule 10 interface eth0 weight 10
+   set load-balancing wan rule 10 interface eth1 weight 1
+
+Example 3: Failover based on rule order
+---------------------------------------
+
+The previous example used the failover command to send traffic thorugh
+eth1 if eth0 fails. In this example failover functionality is provided
+by rule order.
+
+Overview
+^^^^^^^^
+Two rules will be created, the first rule directs traffic coming in
+from eth2 to eth0 and the second rule directs the traffic to eth1. If
+eth0 fails the first rule is bypassed and the second rule matches,
+directing traffic to eth1.
+
+Create rule order based configuration
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+We keep the configurtation from the previous example, delete rule 10
+and create the two new rules as described:
+
+.. code-block:: none
+
+   delete load-balancing wan rule 10
+   set load-balancing wan rule 10 inbound-interface eth2
+   set load-balancing wan rule 10 interface eth0
+   set load-balancing wan rule 20 inbound-interface eth2
+   set load-balancing wan rule 20 interface eth1
+
+Example 4: Failover based on rule order - priority traffic
+----------------------------------------------------------
+
+A rule order for prioritising traffic is useful in scenarios where the
+secondary link has a lower speed and should only carry high priority
+traffic. It is assumed for this example that eth1 is connected to a
+slower connection than eth0 and should prioritise VoIP traffic.
+
+Overview
+^^^^^^^^
+A rule order for prioritising traffic is useful in scenarios where the
+secondary link has a lower speed and should only carry high priority
+traffic. It is assumed for this example that eth1 is connected to a
+slower connection than eth0 and should prioritise VoIP traffic. 
+
+Create rule order based configuration with low speed secondary link
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+We keep the configuration from the previous example, delete rule 20 and
+create a new rule as described: 
+
+.. code-block:: none
+
+   delete load-balancing wan rule 20
+   set load-balancing wan rule 20 inbound-interface eth2
+   set load-balancing wan rule 20 interface eth1
+   set load-balancing wan rule 20 destination port sip
+   set load-balancing wan rule 20 protocol tcp
+   set protocols static route 0.0.0.0/0 next-hop 11.22.33.1
+
+Example 5: Exclude traffic from load balancing
+----------------------------------------------
+
+In this example two LAN interfaces exist in different subnets instead
+of one like in the previous examples:
+
+.. image:: /_static/images/Wan_load_balancing_exclude1.png                      
+   :width: 80%                                                          
+   :align: center                                                       
+   :alt: Network Topology Diagram 
+
+Adding a rule for the second interface
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Based on the previous example, another rule for traffic from the second
+interface eth3 can be added to the load balancer. However, traffic meant
+to flow between the LAN subnets will be sent to eth0 and eth1 as well.
+To prevent this, another rule is required. This rule excludes traffic
+between the local subnets from the load balancer. It also excludes
+locally-sources packets (required for web caching with load balancing).
+eth+ is used as an alias that refers to all ethernet interfaces:
+
+.. code-block:: none
+
+   set load-balancing wan rule 5 exclude
+   set load-balancing wan rule 5 inbound-interface eth+
+   set load-balancing wan rule 5 destination address 10.0.0.0/8