ERR_ICANN_NAME_COLLISION

Enterno.io Editorial Team

By Anatoly Oshmanovsky · Updated Apr 18, 2026

Key idea:

ERR_ICANN_NAME_COLLISION — ICANN-level warning. Your internal network uses a domain (.corp, .home, .lan) that became a public TLD after ICANN gTLD expansion (2013+). Now external DNS resolves your internal hostname → confusion. Chrome warns. Fix: rename internal zones to .internal or .arpa (reserved), or explicitly blacklist.

Below: causes, fixes, FAQ.

Try it now — free →

Common Causes

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

Step-by-Step Fix

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

Check SSL Certificate →

Related SSL Errors

CertificateExpiry, issuer, domains (SAN)

ChainIntermediate and root CA validation

TLS ProtocolTLS version and cipher suite

VulnerabilitiesHeartbleed, POODLE, weak ciphers

Why teams trust us

TLS 1.3

supported

Full

CA chain check

<2s

result

30/14/7

days-to-expiry alerts

How it works

Enter domain

TLS chain verified

Expiry date & vulnerabilities

What Does the SSL Check Cover?

SSL/TLS is the encryption protocol that protects data between the browser and server. Our tool analyzes the certificate, chain of trust, TLS version, and knownvulnerabilities.

Certificate Details

Issuer, validity period, signature algorithm, covered domains (SAN), and validation type (DV/OV/EV).

Chain of Trust

Full chain verification: from leaf certificate through intermediates to root CA.

TLS Analysis

Protocol version (TLS 1.2/1.3), cipher suites, Perfect Forward Secrecy (PFS) support.

Expiry Alerts

Set up a monitor — get Telegram and email alerts 30/14/7 days before expiration.

DV vs OV vs EV Certificates

DV (Domain Validation)

Confirms domain ownership only
Issued in minutes automatically
Free via Let's Encrypt
Suitable for most websites
Most common certificate type

OV / EV

Organization (OV) or Extended Validation (EV)
Issued in 1-5 business days
Costs $50 to $500/year
For finance, e-commerce, government sites
Increases user trust

Who uses this

DevOps

SSL certificate monitoring

Security

TLS config audit

SEO

HTTPS as ranking factor

E-commerce

customer trust

Common Mistakes

❌

Expired certificateBrowsers block sites with expired SSL. Set up auto-renewal or monitoring.

❌

Incomplete certificate chainWithout intermediate CA, some browsers and bots cannot verify the certificate.

❌

Mixed content on HTTPS siteHTTP resources on an HTTPS page — the browser lock icon disappears, reducing trust.

❌

Using TLS 1.0/1.1Legacy TLS versions have known vulnerabilities. Use TLS 1.2+ or 1.3.

❌

Domain mismatch in certificateThe certificate must cover all site domains, including www and subdomains.

Best Practices

✓

Set up auto-renewalLet's Encrypt + certbot with cron — certificate renews automatically every 60-90 days.

✓

Enable HSTSStrict-Transport-Security header forces browsers to always use HTTPS.

✓

Use TLS 1.3TLS 1.3 is faster (1-RTT handshake) and safer — legacy ciphers removed.

✓

Monitor expiration datesCreate a monitor on Enterno.io — get notified well before expiration.

✓

Verify chain after renewalAfter certificate renewal, confirm that intermediate certificates are installed.

Get more with a free account

SSL certificate monitoring, check history and alerts 30 days before expiry.

Learn more

Research

TLS 1.3 Adoption 2026: Growth Pace

Errors

Frequently Asked Questions

Which TLDs currently "collide"?

.corp, .home, .mail, .office — NOT in public use but reserved by ICANN. Safer: .internal (proposed reserved), .home.arpa, .localhost.

Is this a security risk?

Yes: attacker can register a .corp domain, resolve internal names to malicious IPs, MITM.

Does Chrome specifically block?

Chrome warns, does not block. But may treat as suspicious for certain workflows.

Reserved TLDs 2026?

.internal (IETF draft), .test, .localhost, .invalid, .example — safe. Anything else — ideally check the public registry.