Load balancing DNS service

This application note is intended to help you to configure the Aloha to load-balance Domain Name Servers (DNS).


Objective

Ensure high availability of a DNS service.

Reduce DNS resolution latency when the first DNS server is failing.


Constraints

You must have at least 2 DNS servers.


Complexity

1


Versions

v4.1 and later

ALOHA load balancer Load balancing DNS service


Target network diagram

Standard architecture, as bellow:


Context

The clients will use the DNS service on the IP 192.168.0.100.

The Aloha load balance traffic to the two DNS servers 192.168.1.10 and 192.168.1.11.

The Aloha is configured in NAT mode using LVS/layer 4 load balancing service.


Layer 4 LB configuration

On the GUI, click on LB Layer 4 tab, then add the configuration below:

director dns 192.168.0.100:53
	balance roundrobin
	mode nat
	check timeout 2 interval 5
	option tcpcheck
	server server1 192.168.1.10:53 weight 10 check
	server server2 192.168.1.11:53 weight 10 check

Click on [OK], then [Apply].

Note: you need to allow TCP protocol on your DNS server for the health check.

LVS service configuration

If your lvs service is not configured to automatic startup when the Aloha boots up, then go in the Service tab of the GUI and click on the lvs setup icon .

If there is a line “no autostart”, then delete it.

Click on [OK] then [Close]

Then restart the lvs service by clicking on the restart icon .