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ZyWALL 110/310/1100 Series User’s Guide 177
CHAPTER 8
Trunk
8.1 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.
8.1.1 What You Can Do in this Chapter
•Use the Trunk summary screen (Section 8.2 on page 180) to configure link sticking and view the
list of configured trunks and which load balancing algorithm each trunk uses.
•Use the Add Trunk screen (Section 8.2.1 on page 181) to configure the member interfaces for a
trunk and the load balancing algorithm the trunk uses.
•Use the Add System Default screen (Section 8.2.2 on page 183) to configure the load
balancing algorithm for the system default trunk.
8.1.2 What You Need to Know
• 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.