User manual

Chapter 14 Trunks

ZyWALL USG 300 User’s Guide

365

2 The ZyWALL is using active/active load balancing. So when LAN user A tries to

access something on the server, the request goes out through ge3.

3 The server finds that the request comes from ge3’s IP address instead of ge2’s IP

address and rejects the request.

If link sticking had been configured, the ZyWALL would have still used ge2 to send

LAN user A’s request to the server and server would have given the user A access.

Load Balancing Algorithms

The following sections describe the load balancing algorithms the ZyWALL can use

to decide which interface the traffic (from the LAN) should use for a session

. The

available bandwidth you configure on the ZyWALL refers to the actual bandwidth

provided by the ISP and the measured bandwidth refers to the bandwidth an

interface is currently using.

Least Load First

The least load first algorithm uses the current (or recent) outbound bandwidth

utilization of each trunk member interface as the load balancing index(es) when

making decisions about to which interface a new session is to be distributed. The

outbound bandwidth utilization is defined as the measured outbound throughput

over the available outbound bandwidth.

Here the ZyWALL has two WAN interfaces connected to the Internet. The

configured available outbound bandwidths for WAN 1 and WAN 2 are 512K and

256K respectively.

Figure 291 Least Load First Example

The outbound bandwidth utilization is used as the load balancing index. In this

example, the measured (current) 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.

2. In the load balancing section, a session may refer to normal connection-oriented, UDP or SNMP2 traffic.