ZyXEL Communications 110, 1100, 310 Inbound Load Balancing, 17.1 Inbound Load Balancing Overview, Inbound LB

17

Inbound Load Balancing

17.1 Inbound Load Balancing Overview

Inbound load balancing enables the ZyWALL to respond to a DNS query message with a different IP address for DNS name resolution. The ZyWALL 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 (Z)’s WAN1 with an IP address of 1.1.1.1. The ZyWALL 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 responds to it with the WAN1’s IP address, 1.1.1.1, since WAN1 has the least load this time.

Figure 145 DNS Load Balancing Example

		A: Where is		D
		www.example.com?
		Z: It’s 2.2.2.2.
W	1.1.1.1	2			1
			Internet
	2.2.2.2	3
	Z
		B: Where is		D
		www.example.com?
		Z: It’s 2.2.2.2.				1
W	1.1.1.1	2

3 Internet

2.2.2.2

Z

A:Where is www.example.com?

D:Ask 1.1.1.1.

A

B:Where is www.example.com?

D:Ask 1.1.1.1.

B

17.1.1What You Can Do in this Chapter

•Use the Inbound LB screen (see Section 17.2 on page 248) to view a list of the configured DNS load balancing rules.

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ZyWALL 110/310/1100 Series User’s Guide