ZyXEL Communications USG60 - DNS Inbound LB; DNS Inbound Load Balancing Overview; What You Can Do in this Chapter; Chapter 19 DNS Inbound LB

ZyWALL/USG Series User’s Guide
427
CHAPTER 19
DNS Inbound LB
19.1 DNS 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 302 DNS Load Balancing Example
19.1.1 What You Can Do in this Chapter
•Use the Inbound LB screen (see Section 19.2 on page 428) to view a list of the configured DNS
load balancing rules.
Internet
Where is
www.example.com?
Ask 1.1.1.1.
A:
D:
A
D
1.1.1.1
2.2.2.2
W
Z
Where is
www.example.com?
It’s 2.2.2.2.
A:
Z:
1
2
3
Internet
B
D
1.1.1.1
2.2.2.2
W
Z
1
2
3
Where is
www.example.com?
Ask 1.1.1.1.
B:
D:
Where is
www.example.com?
It’s 1.1.1.1
B:
Z: