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SonicOS Enhanced 4.0 Administrator Guide
About Source and Destination IP Address Binding
When you establish a connection with a WAN, you can create multiple interfaces, dividing up
the task load over these interfaces. There are both Primary and Secondary WAN interfaces.
This task distribution model maintains high performance, ensuring that one interface does not
become an impasse to the point where it blocks traffic from passing. This process is WAN Load
Balancing.
While WAN Load Balancing addresses performance challenges, it can create other problems,
including losing track of sessions. Session confusion can occur because some applications fail
to adequately track multiple user sessions Load Balanced on multiple interfaces. These
applications treat incoming packets as originating from different users because they use IP
addresses to differentiate user sessions instead of application-layer user identification tags.
To ensure that you have proper connectivity in all applications, SonicWALL provides a feature
called Source and Destination IP Addresses Binding, a solution that maintains a consistent
mapping of traffic flows with a single outbound WAN interface.
Setting Up WAN Failover and Load Balancing
Perform the following steps to configure WAN Failover and Load Balancing on the SonicWALL
security appliance:
1. “Configuring an Interface as a Secondary WAN Port” on page 182
2. “Creating a NAT Policy for the Secondary WAN Port” on page 183
3. “Activating WAN Failover and Selecting the Load Balancing Method” on page 184
4. “Configuring WAN Interface Monitoring” on page 186
5. “Configuring WAN Probe Monitoring” on page 187
Configuring an Interface as a Secondary WAN Port
On Network > Interfaces page, configure the chosen port to be in WAN zone, and enter in the
correct address settings provided by the Secondary ISP. In the example, the SonicWALL
security appliance is acquiring its secondary WAN address dynamically from ISP #2, using
DHCP. Any interface added to the WAN zone by default creates a NAT Policy allowing internal
LAN subnets to NAT out this Secondary WAN interface.