ERR_ICANN_NAME_COLLISION

• Internal AD domain like .corp became a public gTLD
• Old split-horizon DNS setup with .home, .lan
• /etc/hosts entries with common names
• Resolver tried public DNS before internal
• NetBIOS broadcast names

1. Rename internal zone to .internal, .home.arpa (RFC 8375)
2. Strict DNS suffix order: internal first
3. Or forbid resolver for public TLDs on endpoints
4. AD migration — a big project (prepare)
5. Temporary: /etc/hosts manual entries for critical hosts

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• ERR_SSL_PROTOCOL_ERROR
• NET::ERR_CERT_AUTHORITY_INVALID
• SSL Handshake Failed
• All SSL errors

The ERR_ICANN_NAME_COLLISION error occurs when a domain name resolves to an internal TLD (Top-Level Domain) that collides with a public TLD, causing DNS resolution failures. This typically affects private networks or local test environments where domains are misconfigured or overlap with existing ICANN TLDs. To resolve this, ensure your internal TLDs do not conflict with public TLDs by using custom or non-ICANN TLDs.

The ERR_ICANN_NAME_COLLISION error arises when a domain name used in a private network conflicts with a public TLD registered with ICANN (Internet Corporation for Assigned Names and Numbers). This conflict can occur when:

• Using a non-standard TLD in a local environment that is also a valid public TLD, such as .local, .test, or .home.
• Misconfiguration in DNS settings, causing the internal network to resolve the domain to the public TLD.
• A domain name that is not properly segmented between internal and external usage.

Such collisions can lead to issues in DNS resolution, affecting the accessibility of services hosted on the conflicting domain.

To resolve the ERR_ICANN_NAME_COLLISION error, it is essential to implement best practices in domain naming and DNS configuration. Below are several strategies you can employ:

1. Use Custom TLDs: Instead of using standard TLDs, opt for custom TLDs that are not registered with ICANN. For example, instead of using .local, consider using .testlocal or .example.
2. DNS Configuration: Ensure your DNS settings do not point to conflicting public TLDs. You can use the following command to check your current DNS settings:

nslookup yourdomain.test

Replace yourdomain.test with your actual domain. If this resolves to a public IP, you may need to adjust your DNS records.

1. Modify Hosts File: For local testing, you can add entries to your hosts file to avoid DNS resolution issues. On Windows, edit C:\Windows\System32\drivers\etc\hosts, and on Linux or macOS, edit /etc/hosts. Add lines like:

127.0.0.1 yourdomain.test

This will force the system to resolve yourdomain.test to your local machine.

1. Network Segmentation: If your organization has multiple environments (development, testing, production), ensure that they are properly segmented and that domain names are unique across these environments to prevent collisions.

By implementing these practices, you can minimize the risk of encountering the ERR_ICANN_NAME_COLLISION error and ensure smooth operation of your web services.