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SonicOS Enhanced 4.0 Administrator Guide
CHAPTER 16
Chapter 16: Setting Up WAN Failover and Load
Balancing

Network > WAN Failover & Load Balancing

WAN Failover and Load Balancing allows you to designate the one of the user-assigned
interfaces as a Secondary or backup WAN port. The secondary WAN port can be used in a
simple active/passive setup, where traffic is only routed through the secondary WAN port if the
primary WAN port is down and/or unavailable. In this chapter, this feature is referred to as basic
failover. This allows the SonicWALL security appliance to maintain a persistent connection for
WAN port traffic by failing over to the secondary WAN port. The primary and secondary WAN
ports can also be used in a more dynamic active/active setup, where the administrator can
choose a method of dividing outbound traffic flows between the Primary fixed WAN port and the
user-assigned Secondary WAN port. This latter feature is referred to as load balancing.

WAN Failover Caveats

• WAN Failover and Load Balancing applies to outbound-initiated traffic only; it cannot be
used to perform inbound Load Balancing functions, such as what a content switching or
Load Balancing appliance provides.
• Make sure that the SonicWALL security appliance has the proper NAT policies for the
Secondary WAN interface an incorrect or missing NAT Policy for the Secondary WAN port
is the most common problem seen when configuring WAN Failover & Load Balancing.
• The Primary and Secondary WAN ports cannot be on the same IP subnet; each WAN
connection must be on unique IP subnets in order to work properly
• You cannot use the WAN failover feature if you have configured the SonicWALL security
appliance to use Transparent Mode in the Network > Interfaces page.