ZyXEL Communications ZYWALL USG 20 Manual page 291

Spillover
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
interface. This fully utilizes the bandwidth of the first interface to reduce Internet
usage fees and avoid overloading the interface.
Finding Out More
• See Section 6.5.4 on page 96
• See Section 7.3 on page 113
• See Section 12.4 on page 295
ZyWALL USG 20/20W User's Guide
for related information on the Trunk screens.
for an example of how to configure load balancing.
for more background information on trunks.
Chapter 12 Trunks
291