On February 1, 2019, the largest DNS manufacturers (Bind, Unbound, PowerDNS and Knot DNS) will publish new versions of DNS recursive software without any temporary fixes. Temporary fixes deviate from the standard and are a response to the wrong behavior of DNS servers. Unless software updates are available, they can either make the domains unreachable or slow.

Misconduct that does not conform to the EDNS standard (RFC2671, RFC6891) involves exceeding the time limits for response, incorrect switching of bits, delay in response, etc.

EDNS standard allows for a number of improvements and functionalities of DNSSEC, cookies, geolocation and other security extensions.

For these reasons manufacturers of DNS software and DNS service providers (Cloudflare, Google, etc.) allow all interested parties to verify their domain at:
https://dnsflagday.net/

You can also check the domain on the ISC website. Their tool further demonstrates the successfully completed tests and errors of an inadequate, unexpected response. In addition to online verification you can also find examples for command line on the link below:
https://ednscomp.isc.org/

For .si zone, we used the tool created by the Czech TLD registry. The tool is suitable for viewing entire zones and not individual domains. Available on:
https://gitlab.labs.nic.cz/knot/edns-zone-scanner/

The results of .si zone test shows that 534 domains are in danger of becoming unreachable or slow after February 1, 2019. If you find that your domain is among them, please contact dns@register.si for details or contact your registrar.