By default when you set up a virtual WAN link source IP based load balancing is selected and traffic is load balanced among the interfaces added to virtual WAN link configuration. You can change the load balancing method to weighted load balancing, spill-over load balancing or source-destination IP load balancing. Selecting a different load balancing method may also require configuring the interfaces added to the virtual WAN link to add weights (for weighted load balancing) or to set spillover thresholds.