What is DNS Server Load Balancing?

DNS Server Load Balancing is an architecture where Domain Name System (DNS) servers are placed behind a Server Load Balancing system. DNS requests are distributed, or load balanced, across a group of DNS servers. This provides a highly available and high performing DNS infrastructure.

DNS technologies provide a built-in load balancing solution based on the DNS protocol specification. Multiple DNS servers are often deployed, and clients performing DNS queries are presented a list of IP addresses for every DNS server. The DNS client protocol will attempt to query the first DNS server, and if this query fails, will fail-over and attempt the query on the next DNS server.

This DNS standard solution works well enough for most network environments. The downside with the standard DNS failover mechanism is when one or more of the DNS servers is not responding to DNS queries, the client will pause until the request times out. This timeout period depends on the client system. Typical timeout periods are 15 seconds or more. In modern networks, 15 seconds is an extremely long time.

There are classes of network infrastructures where the standard DNS failover mechanism is unacceptable. These environments include:

DNS Server Load Balancing Benefits

DNS Servers placed behind Server Load Balancers or Application Delivery Controllers is a “best in class”architecture for mission critical infrastructures. DNS queries are simple UDP connections on port 53 and relatively simple to deploy. The benefits of this architecture include:

Related Terms

How A10 Networks Can Help

A10 Networks Thunder Series of Application Delivery Controllers is deployed in most of the world’s largest carrier network and service provider networks.

A10 devices are built using an in-depth strategy, with key protections integrated within our Thunder Series ADCs. Our ADCs are compatible with a variety of different firewall vendors, allowing you to deploy our devices right away with your existing corporate defense systems and adequately secure your network.

Learn more about the A10 portfolio of high-performance ADCs. Download the white paper Evolution of ADCs: The A10 Advantage Over Legacy Load Balancers.


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July 10, 2018

About Robert Keith

Robert has 30 years of experience in IT technology development and infrastructure management. He was the founder of several infrastructure ventures including Intellivence, MaxSP, Sentrik and most recently was the CTO of Iron Networks. As CTO of Iron Networks in San Jose, CA, he worked directly with many companies in the Silicon Valley to design and architect network, security, and cloud solutions. He worked directly with Microsoft engineering in the design of their cloud architectures including storage, Hyper-V, Systems Center and Virtual Networking. He also worked directly with Hortonworks to design a Hadoop deployment and management system using CentOS and many layered software packages. READ MORE