DNS Flag Day – 1 February 2019

DNS Flag Day
Domain Name System
by Mick Begley
31 Jan 2019
1 minutes to read

What is DNS Flag Day?

From 1 February 2019 changes will be rolled out to the Domain Name System (DNS) software. Named, DNS Flag Day, this is to prepare the DNS for the deployment of new features.

However, the knock-on effect is that some domain names will break for anyone who is using a non-compliant DNS setup.

We have been scanning the .ie zone over the past few months and reached out to Registrars and domain holders to assist them in moving their DNS to a compliant setup. Currently there are just under 0.4% that are not yet compliant.

Technical information

If your authoritative nameservers do not accept DNS queries over TCP (port 53) they are EDNS non-compliant.

This is problematic as the major Opensource DNS providers will be removing workarounds from their codebase that allow for such domains to be resolved from 1 February.

Likewise, a number of major commercial resolvers such as Google (, Cloudflare ( and Quad-9 ( will implement this change.

What can I do to check my domain?

You can test your domain and read more about the upcoming DNS Flag Day at the below links:



Please contact your Registrar or DNS provider straight away if you see any issues with your domain.


If you have any questions about your .ie domain name and DNS Flag Day, please email noc@iedr.ie