Inbound Load Balancing; Inbound Load Balancing Overview; What You Can Do In This Chapter - ZyXEL Communications USG40 User Manual

16.1 Inbound Load Balancing Overview

Inbound load balancing enables the ZyWALL/USG to respond to a DNS query message with a
different IP address for DNS name resolution. The ZyWALL/USG checks which member interface
has the least load and responds to the DNS query message with the interface's IP address.
In the following figure, an Internet host (A) sends a DNS query message to the DNS server (D) in
order to resolve a domain name of www.example.com. DNS server D redirects it to the ZyWALL/
USG (Z)'s WAN1 with an IP address of 1.1.1.1. The ZyWALL/USG receives the DNS query message
and responds to it with the WAN2's IP address, 2.2.2.2, because the WAN2 has the least load at
that moment.
Another Internet host (B) also sends a DNS query message to ask where www.example.com is. The
ZyWALL/USG responds to it with the WAN1's IP address, 1.1.1.1, since WAN1 has the least load this
time.
Figure 204 DNS Load Balancing Example
W
W

16.1.1 What You Can Do in this Chapter

• Use the Inbound LB screen (see
load balancing rules.
C

Inbound Load Balancing

Where is
A:
www.example.com?
Z:
It's 2.2.2.2.
2
1.1.1.1
2.2.2.2 3
Z
Where is
B:
www.example.com?
Z:
It's 1.1.1.1
2
1.1.1.1
3
2.2.2.2
Z
Section 16.2 on page
ZyWALL/USG Series User's Guide
296
HAPTER
D
Where is
A:
www.example.com?
D:
1 Ask 1.1.1.1.
Internet
D
Where is
B:
www.example.com?
D:
1
Ask 1.1.1.1.
Internet
297) to view a list of the configured DNS
1 6
A
B