ZyXEL Communications 5 Series User Manual

 Chapter 9 WAN Screens

ZyWALL 5/35/70 Series User’s Guide

To configure load balancing on the ZyWALL, click NETWORK > WAN in the navigation 
panel. The WAN General screen displays by default. Select Active/Active Mode under 
Operation Mode to enable load balancing on the ZyWALL. 

The WAN General screen varies depending on what you select in the Load Balancing 
Algorithm field.

The least load first algorithm uses the current (or recent) outbound and/or inbound bandwidth 
utilization of each WAN interface as the load balancing criteria for making decisions on how 
how to route traffic. The outbound bandwidth utilization is defined as the measured outbound 
throughput over the available outbound bandwidth. The inbound bandwidth utilization is 
defined as the measured inbound throughput over the available inbound bandwidth. The two 
ratios are indexes used to calculate which WAN interface is less utilized at the time. A new 
LAN-originated session is distributed to the less utilized WAN interface.

The following figure depicts an example where both the WAN interfaces on the ZyWALL are 
connected to the Internet. The configured available outbound bandwidths for WAN 1 and 
WAN 2 are 512K and 256K respectively.

Figure 99   Least Load First Example 

If the outbound bandwidth utilization is used as the load balancing index and the measured 
outbound throughput of WAN 1 is 412K and WAN 2 is 198K, the ZyWALL calculates the 
load balancing index as shown in the table below. 

Allow Trigger Dial

Select this option to allow NetBIOS packets to initiate calls.

Apply

Click Apply to save your changes back to the ZyWALL.

Reset

Click Reset to begin configuring this screen afresh.

Table 35   NETWORK > WAN > General (continued)