ZyXEL Communications ZyWall ATP series User Manual page 288

• If that interface's connection goes down, the Zyxel Device can still send its traffic through another
interface.
• You can define multiple trunks for the same physical interfaces.
LAN user A logs into server B on the Internet. The Zyxel Device uses wan1 to send the request to server B.
1
The Zyxel Device is using active/active load balancing. So when LAN user A tries to access something on
2
the server, the request goes out through wan2.
The server finds that the request comes from wan2's IP address instead of wan1's IP address and rejects
3
the request.
If link sticking had been configured, the Zyxel Device would have still used wan1 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 Zyxel Device can use to decide which
interface the traffic (from the LAN) should use for a session. In the load balancing section, a session may
refer to normal connection-oriented, UDP or SNMP2 traffic
the Zyxel Device 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 Zyxel Device 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 197 Load Balancing 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 Zyxel Device calculates the
load balancing index as shown in the table below.
Chapter 9 Interfaces
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The available bandwidth you configure on
.