IIS Failover With DNS Round Robin


  1. DNS Round Robin
    1. How it works
  2. Steps by Steps
    1. Shared Folders & Permissions
    2. DNS Setup
    3. Web Server Setup
    4. Verify
  3. References
  4. Related Links

Note about how to achive Failover and High Availability with IIS.

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DNS Round Robin

We will have two idependent virtual machines, both of them installed IIS. And we will have a shared folder from another virtual machine for these IIS Servers.This shared folder has html, asp, images and etc files.

First, we set up the new site in web server1, and then we set up another site in web server2. Both web server1 & web server 2 location point to the shared folder.

The Application pool must have permissions to access files from shared folder.

then, we add two DNS record like:

A demo.sdwh.local 192.168.100.101
A demo.sdwh.local 192.198.100.102

How it works

When client request demo.sdwh.local, DNS will reply all of its record. Then client side browser try one, and keep using the worked server ip.

Once the web server fail (IIS stop or Windows Server stop), then client side will get no response, and user will press Refresh, the browser will try to use another record until it works.

The DNS round robin works best if the server is actually off not just slow/timing out as the modern browser can move to the next very quickly.
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Steps by Steps

Shared Folders & Permissions

DNS Setup

Web Server Setup

Add Site
File Location
Site Identity
Application Identity

Verify

  • Check Which Server Response by ASP script
  • Check Failover by Server Crash
  • Check Failover by IIS Crash
  • Cehck Failover by Application Pool Crash

References

Overview: Build a Web Farm with IIS Servers | docs.microsoft

How to configure DNS round robin for web server failover

IIS Notes

IIS Security Configuration)