What You Need To Know - ZyXEL Communications ZYWALL USG 20 Manual

Chapter 12 Trunks

12.1.2 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.
• If that interface's connection goes down, the ZyWALL can still send its traffic
through another interface.
• You can define multiple trunks for the same physical interfaces.
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
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.
Weighted Round Robin
The Weighted Round Robin (WRR) algorithm is best suited for situations when the
bandwidths set for the two WAN interfaces are different. Similar to the Round
Robin (RR) algorithm (see
(WRR) algorithm sets the ZyWALL to send traffic through each interface in turn. In
addition, the interfaces are assigned weights. An interface with a larger weight
gets more of the traffic than an interface with a smaller weight.
2. In the load balancing section, a session may refer to normal connection-oriented, UDP or SNMP2 traffic.
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Section 12.4 on page 295), the Weighted Round Robin
ZyWALL USG 20/20W User's Guide
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