Implement Inbound Server Load Balance

Zyxel_Kevin Posts: 803  Zyxel Employee
First Anniversary 10 Comments Friend Collector First Answer
edited August 2022 in Networking

Inbound Server Load Balance

For load Balance or redundant purpose, some enterprises  might have more than one ISP or Web Server to handle incoming service requests. This article will explain how to achieve the goal on Zyxel Firewall.

Before Begin

Firewall uses Algorithm to respond to a DNS query with the IP address in Domain A record. To make it more efficient, Firewall has to act as Name Server(NS)

Set up DNS Inbound LB

CONFIGURATION > Network > DNS Inbound LB 

In this example, we use Weighted Round Robin method in DNS Load Balancing to send the ISP Addresses (, to the DNS query senders. When the load balancing algorithm cannot find any available interface, Zyxel Device will respond to the DNS query with the Failover IP Address.

Set up Virtual Server Load Balancer

CONFIGURATION -> NAT -> Virtual Server Load Balancer

Set Destination NAT for two WAN IP. In this field , you can set Load Balancing Algorithm and heathy check. The Zyxel Device periodically sends a request to each real server. This request ensures that the server is available. Once the healthy check failed, it won't perform NAT process for the failed one.

Test Result

With Weighted Round Robin method. First query response, second query response

MONITOR -> Network Status -> Virtual Server LB

In this field, you can monitor each WAN IP and real server usage. Each connection is balanced between two WAN IPs and two real servers.