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ZyWALL USG 100/200 Series User’s Guide
269
CHAPTER 11
Trunks
11.1 Overview
Use trunks for WAN traffic load balancing to increase overall network throughput and
reliability. Load balancing divides traffic loads between multiple interfaces. This allows you
to improve quality of service and maximize bandwidth utilization for multiple ISP links.
Maybe you have two Internet connections with different bandwidths. You could set up a trunk
that uses spillover or weighted round robin load balancing so time-sensitive traffic (like video)
usually goes through the higher-bandwidth interface. For other traffic, you might want to use
least load first load balancing to even out the distribution of the traffic load.
Suppose ISP A has better connections to Europe while ISP B has better connections to
Australia. You could use policy routes and trunks to have traffic for your European branch
office primarily use ISP A and traffic for your Australian branch office primarily use ISP B.
Or maybe one of the ZyWALL's interfaces is connected to an ISP that is also your Voice over
IP (VoIP) service provider. You can use policy routing to send the VoIP traffic through a trunk
with the interface connected to the VoIP service provider set to active and another interface
(connected to another ISP) set to passive. This way VoIP traffic goes through the interface
connected to the VoIP service provider whenever the interface’s connection is up.
11.1.1 What You Can Do in the Trunk Screens
• Use the Trunk summary screen (Section 11.2 on page 272) to configure link sticking and
view the list of configured trunks and which load balancing algorithm each trunk uses.
• Use the Trunk Edit screen (Section 11.2.1 on page 273) to configure which interfaces
belong to each trunk and the load balancing algorithm each trunk uses.
11.1.2 What you Need to Know About Trunks
• Add WAN interfaces to trunks to have multiple connections share the traffic load.
• If one WAN interface’s connection goes down, the ZyWALL sends traffic through
another member of the trunk.
• For example, you connect one WAN interface to one ISP and connect a second WAN
interface to a second ISP. The ZyWALL balances the WAN traffic load between the
connections. If one interface's connection goes down, the ZyWALL can automatically
send its traffic through another interface.
You can also use trunks with policy routing to send specific traffic types through the best
WAN interface for that type of traffic.