ERR_ADDRESS_UNREACHABLE — Server Unreachable

Enterno.io Editorial Team

ERR_ADDRESS_UNREACHABLE: Diagnosis

By Anatoly Oshmanovsky · Updated Apr 17, 2026

Key idea:

ERR_ADDRESS_UNREACHABLE — Chrome could not establish a TCP connection to the IP. Below the TLS layer. Causes: DNS returned wrong IP, routing issue (server down/no internet), firewall in the path, ISP blocks the range. Fix: ping/traceroute to diagnose.

This error blocks HTTPS access. Below: causes, fixes, working config, FAQ.

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Common Causes

DNS returned stale IP after server migration
Server fully down (hardware failure, DC outage)
Firewall (server-side or client-side) drops SYN
ISP-level block (regional censorship, .onion)
Routing issue: trace stops at an intermediate hop

Step-by-Step Fix

Check resolution: nslookup example.com 1.1.1.1 — right IP?
Ping: ping example.com — any reply?
Traceroute: traceroute example.com — where does it die?
Enterno Traceroute visualizes the chain
Try via VPN — if it works = ISP block

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

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TLS 1.3

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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.

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

Learn more

How-to

Glossary

Research

TLS Cipher Suites 2026: Distribution Report

Errors

Alternatives

Frequently Asked Questions

How is it different from ERR_CONNECTION_REFUSED?

REFUSED = server sent RST (no listener). UNREACHABLE = IP does not respond at all (network issue).

Is the error only on my side?

Check via <a href="/en/ping">Enterno Ping</a> from multiple regions. Only your network — your problem.

How long to recover?

Depends on cause. DC outage — hours. DNS propagation — 5-60 min. Hardware — more complex.

Error on mobile but not desktop?

Mobile carriers have different DNS/routing. Try 8.8.8.8 on phone.