What is DNS Failover and How Does It Work?

Failover has been the cornerstone of DNS Made Easy’s routing services for nearly a decade now. Even all these years later, DNS Made Easy still processes over ___ Failover events a day.

Failover is a powerful yet simple tool that allows you to change the IP or hostname your traffic is pointed to in the event your primary endpoint is downed.

Terms

Before we get into the technical stuff, let’s go over some basic terminology.

Query: The request an end-user makes to resolve a domain to an IP address or hostname.

Endpoint: This can be either an IP address (like 172.08.260.1) or a hostname (like dnsmadeeasy.com).

You will need a basic knowledge of how a DNS queries are answered. Here’s a quick refresher.

How It Works

Above, is how an authoritative name server would answer a querying client. We’re going to use an A record, which maps a domain (example.com) to an IP address (198.168.1.1).

Now if we add failover to this A record, it’ll look something like this:

If the primary IP address is up, traffic will be routed to the primary IP. DNS Made Easy monitoring nodes check your primary IP’s availability every 2–4 minutes. If the IP fails to respond from two different locations, it is considered down. Traffic will automatically be served by the secondary IP address and an email alert will notify the account admin of the Failover event.

Monitoring nodes will continue to check the availability of the downed primary IP until it is available again. Traffic will automatically be rerouted back to the primary IP.

You can add up to 4 different backup IP addresses in a Failover configuration. That means, if you secondary IP is unavailable, traffic will be answered by your tertiary IP address and so on.

You can learn how to set up DNS Failover for your DNS Made Easy account by following the tutorial here.

Originally published at DNS Made Easy News.