Blog - Switching Servers

Refract DNS was designed with the intention of making it easy to change the IP address of a domain when working in environments with multiple load balanced servers. In this blog post we will explore how to do this.

The Server Setup

In my fictional environment I have 4 servers that are load balanced. The servers deliver a fictional domain called "cats.refractdns.com" (cats are the reason the internet exists). The server setup is shown below:

During normal operation an IP lookup of "cats.refractdns.com" will return the IP address 148.251.177.228:

In Refract DNS I have setup an override for each of my servers. Currently they are all disabled:

When I make a request to cats.refractdns.com any of the 4 servers could respond.

Diagnosing Issues

From time to time, one of the servers has a bad day (we have all been here) and I need to diagnose and solve the problem.

Today server 2 has decided to have a bad day and I need to make some test requests to cats.refractdns.com which must go to server 2 to diagnose the issue.

If I make the requests to cats.refractdns.com at the moment, I am not guaranteed to hit server 2; any of the four servers could respond. I therefore need to override the upstream DNS with the IP address of server 2.

In Refract DNS this is really easy, just a single click is required:

Now all my requests will go directly to server 2:

I want to compare requests that are made to server 2 with requests made to server 3 to help my diagnose the issue. Therefore I need to change the DNS again to point at server 3. As before, with Refract DNS this is very easy.

By enabling the server 3 override in Refract DNS it will automatically disable the server 2 override:

Instantly the IP address is changed:

No need to search through the host file trying to find the correct entries to comment in or out!

Everything is Fixed

I have finished diagnosing the issue on server 2 and it is now operating as expected. I now need to disable my DNS overrides so that my requests go back via the load balancer.

Again a single click disables the server 2 override:

This allows the upstream DNS server to return the desired IP address:

Summary

Refract DNS is designed to make working with large numbers of servers very simple. It allows you to easily organise, find and override DNS settings which saves you time and frustration.

Mike - March 2019

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