ICANN seeks community input on IPv6 name collision study

The Internet Corporation for Assigned Names and Numbers (ICANN) has opened a public consultation on a new technical study designed to improve how it prevents ‘name collisions’ – a phenomenon that occurs when private domain names unintentionally overlap with names on the public internet. The consultation seeks feedback on a proposal to adopt a specific IPv6 address for use in what is known as ‘controlled interruption,’ a key mitigation measure during the launch of new top-level domains (gTLDs).

Name collisions can occur when internal network systems use domain names that later become publicly registered on the internet, leading to potential confusion or security risks. To mitigate this, ICANN introduced controlled interruption in 2014, a temporary safety measure that allows system administrators to detect and fix conflicts before new domains go live. During this phase, special internet records are inserted so that affected systems receive a local “loopback” address, preventing data from being sent across the internet.

For IPv4 systems, ICANN uses the address 127.0.53.53, which intentionally triggers alerts without causing real connections. However, at the time the mechanism was created, there was no equivalent address for IPv6. This gap was initially not critical because few devices supported IPv6, but with more than 40% of internet hosts now using the protocol, the absence of a solution has become increasingly problematic.

ICANN’s new Name Collision IPv6 Research Study tested several potential IPv6 addresses to identify one that behaves similarly to the existing IPv4 solution. After extensive analysis of Internet Assigned Numbers Authority (IANA) registries and application testing across major operating systems, researchers proposed using ffff::127.0.53.53 as the new IPv6 ‘controlled interruption’ address. The address belongs to a reserved range that prevents it from reaching external networks, ensuring safety during testing.

What is next?

ICANN is now inviting feedback from network operators, technical experts, and the broader internet community on the findings and recommendations of the study. The consultation opened on 20 October 2025 and will remain open until 22 December 2025.

Community input will be used to refine the proposal before ICANN finalises its approach and publishes a report on how controlled interruption will be implemented for IPv6. The decision is an important step in ensuring that the next round of new gTLDs can be introduced safely in an increasingly IPv6-based internet environment.