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Synology NAS | Synology NAS Inspector times out while trying to connect

Synology, Synology NAS, Synology NAS Inspector times out while trying to connect, timeout error

Updated over a month ago

Overview 💥

This article addresses the issue where the Synology NAS Inspector fails with a timeout error while attempting to connect to the configured Synology appliance.
Timeouts usually indicate an underlying communication, authentication, certificate, or configuration issue between the Liongard Agent and the Synology NAS device.

Error Message : 

"Timed out while trying to connect to Synology appliance. Check that appliance is online and verify connectivity over HTTPS via the provided device hostname and port."

Why This Happens 🤔

The timeout indicates that the Agent was unable to establish an HTTPS connection with the Synology NAS. This is commonly caused by one or more of the following:

Top Root Causes :

Category

Possible Cause

Explanation

Network & Connectivity

  • Firewall blocks

  • Incorrect hostname/IP

  • Wrong HTTPS port

  1. Traffic between Agent → Synology is blocked (LAN rules, ACLs, IPS/IDS).

  2. Agent cannot resolve or reach the specified endpoint.

  3. Synology DSM often runs on 5001; custom ports may differ.

Synology Device Issues

  • Device offline / sleep mode

  • DSM not listening on HTTPS

  1. Synology power-saving features can block remote access.

  2. SSL disabled or misconfigured.

Certificate Issues

Self-signed cert not trusted

Agent machine may reject HTTPS handshake.

Version Compatibility

Unsupported DSM version

Liongard supports DSM 6.x and 7.x. Old versions may break API calls.

Steps to Resolve 👨‍💻

1️⃣ Verify Device Is Reachable on the Network

1.1 Ping Test

From the Agent machine, run:

ping <Synology-IP-or-FQDN>

1.2 Port Connectivity Test

Test-NetConnection -ComputerName <hostname> -Port <port>

Expected Result

Interpretation

TcpTestSucceeded = True

Port is reachable ✔

TcpTestSucceeded = False

Firewall, routing, or wrong port ✖

2️⃣ Confirm Web Portal Accessibility from Agent Machine

Using any browser on the machine where Liongard Agent is installed:

https://<hostname>:<port>

You should see:

  • Synology DSM login page

  • No certificate blocking errors

  • Quick page load (<5 seconds)

If it hangs, loads slowly, or errors → connectivity or certificate issue.

3️⃣ Validate Inspector Configuration

Ensure the Inspector template matches your Synology setup:

Field

What to Check

Hostname

Use FQDN or static IP, avoid NetBIOS names.

Port

Default DSM HTTPS port is 5001, unless customized.

Credentials

Ensure correct user/pass with appropriate DSM permissions.

4️⃣ Validate DSM Version Compatibility

Liongard supports:

  • DSM 6.x

  • DSM 7.x

If using DSM 5.x or older, API calls may fail.

Check DSM version: DSM GUI → Control Panel → Info Center → General.

5️⃣ Check Synology Firewall & Security Controls

5.1 Synology Firewall Rules

DSM → Control Panel → Security → Firewall

Ensure:

  • Agent machine IP is allowed

  • HTTPS port rule is enabled

  • No geo-blocking or region restrictions

5.2 Reverse Proxy & Web Services

If using Synology Application Portal reverse proxy, verify the mapping is correct.

6️⃣ SSL/TLS Certificate Handling

If your DSM uses a self-signed certificate, the Agent machine may reject HTTPS.

Fix options:

Option

Description

Import cert into Agent machine’s Trusted Store

Recommended for secure environments

Switch to a Let’s Encrypt certificate

DSM supports auto-renewal

Temporarily disable strict certificate validation

Only if your security policy allows it

7️⃣ Check for IP Allowlisting, ACL, or Geo-Blocking

DSM blocks traffic if configured with:

  • IP Allow Lists.

  • Deny Lists.

  • Country restrictions.

  • Synology Security Advisor rules.

  • 2-step verification enforcement.

Ensure the Agent’s IP is not restricted.

8️⃣ Review Liongard Inspector Logs for Detailed Errors

From the Liongard interface:

  1. Go to the Synology Inspector

  2. Run inspector in Clear-Cache + Debug Mode

  3. Check inspection Logs

  4. Look for:

    • HTTPS handshake failures.

    • Certificate validation errors.

    • TCP timeout messages.

    • Authentication failures.

This helps identify the root cause.

Troubleshooting Table 🚀

Symptom

Possible Cause

Action Required

Timeout immediately (<1 sec)

Host unreachable

Check IP/FQDN, firewall, port forwarding

Timeout after long wait (20–30 sec)

Port blocked

Run Test-NetConnection, validate port

“Certificate not trusted” error

Self-signed cert

Import cert, replace with trusted CA

Browser cannot load DSM login page

DSM offline

Check power, DSM service status

Works in browser but not Inspector

Credential/API issue

Re-enter credentials, check permissions

Best Practices 🤩

  • Use FQDN or a static IP in Inspector config.

  • Keep DSM firmware updated.

  • Document any custom ports or firewall rules.

  • Ensure the Agent machine has stable network access.

  • Avoid wildcard DNS records for NAS devices.

When to Contact Liongard Support 🦁

If the issue persists after completing all steps above, gather the following before contacting support:

Provide:

  • Inspector logs.

  • DSM version.

  • Screenshot of Inspector configuration.

  • Results of:

    • Test-NetConnection

    • Browser test (https://hostname:port)

  • Firewall details.

  • Recent network changes.

This dramatically speeds up resolution.

Reference Documentation 📝

Disclaimer ‼️

We may reference external third-party resources solely as additional guidance.
​Liongard does not own, control, or guarantee the accuracy, security, or reliability of third-party sites. Please use them at your own discretion and risk.

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