ZyXEL Communications 1000 Manual Do Utilizador

Chapter 14 Trunks

ZyWALL USG 1000 User’s Guide

Since WAN 2 has a smaller load balancing index (meaning that it is less utilized 
than WAN 1), the ZyWALL will send the subsequent new session traffic through 
WAN 2.

The Weighted Round Robin (WRR) algorithm is best suited for situations when the 
bandwidths set for the two WAN interfaces are different. Similar to the Round 
Robin (RR) algorithm (see 

), the Weighted Round Robin 

(WRR) algorithm sets the ZyWALL to send traffic through each WAN interface in 
turn. In addition, the WAN interfaces are assigned weights. An interface with a 
larger weight gets more of the traffic than an interface with a smaller weight.

For example, in the figure below, the configured available bandwidth of ge2 is 1M 
and ge3 is 512K. You can set the ZyWALL to distribute the network traffic between 
the two interfaces by setting the weight of ge2 and ge3 to 2 and 1 respectively. 
The ZyWALL assigns the traffic of two sessions to ge2 for every session's traffic 
assigned to ge3.

Figure 268   Weighted Round Robin Algorithm Example

The spillover load balancing algorithm sends network traffic to the first interface in 
the trunk member list until the interface’s maximum allowable load is reached, 
then sends the excess network traffic of new sessions to the next interface in the 
trunk member list. This continues as long as there are more member interfaces 
and traffic to be sent through them.

Suppose the first trunk member interface uses an unlimited access Internet 
connection and the second is billed by usage. Spillover load balancing only uses 
the second interface when the traffic load exceeds the threshold on the first 

Table 78   Least Load First Example 

WAN 1

512 K

412 K

0.8

WAN 2

256 K 

198 K

0.77