ZyWALL ATP Series User’s Guide
371
C
HAPTER
18
DNS Inbound LB
18.1 DNS Inbound Load Balancing Overview
Inbound load balancing enables the Zyxel Device to respond to a DNS query message
with a different
IP address for DNS name resolution. The Zyxel Device 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 Zyxel Device (
Z
)’s WAN1
with an IP address of 1.1.1.1. The Zyxel Device 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 Zyxel
Device responds to it with the WAN1’s IP address, 1.1.1.1, since WAN1 has the least load this time.
Figure 260
DNS Load Balancing Example
18.1.1 What You Can Do in this Chapter
• Use the
Inbound LB
screen (see
) to view a list of the configured DNS load
balancing rules.
• Use the
Inbound LB Add/Edit
screen (see
) to add or edit a DNS load
balancing rule.
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
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:
