Overview 💥
This article helps troubleshoot the following Microsoft SQL Server inspection error seen in Liongard when the SQL Server Inspector cannot connect to the specified SQL Server instance during the connectivity test.
Error Message:
Connectivity test failed. Exception: A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: SQL Network Interfaces, error: 26 - Error Locating Server/Instance Specified)
This error most commonly appears when a named SQL instance is configured incorrectly or cannot be reached from the Liongard Agent.
Why This Happen? 🤔
This is a standard Microsoft SQL Server connectivity error that occurs when the Liongard Agent cannot resolve, locate, or connect to the SQL instance.
Common Root Causes
Cause | Explanation |
Incorrect instance name | Instance name is not in |
SQL Server Browser service stopped | Required to locate named instances |
Remote connections disabled | SQL Server does not allow external connectivity |
Firewall blocked | TCP 1433 or dynamic ports are not allowed |
DNS / network issues | Agent cannot resolve the SQL host |
Instance offline | SQL services are stopped |
Dynamic ports | Named instances often use random ports not allowed in firewall |
Steps to Resolve 👨💻
1️⃣ Validate Instance Name Format
Scenario | Action |
Default instance | Leave the instance field blank (uses |
Named instance | Use |
2️⃣ Verify SQL Server Services
On the SQL Host:
Open SQL Server Configuration Manager
Confirm the following services are running:
Service Name | Required |
SQL Server (InstanceName) | ✅ Yes |
✅ Required only for named instances |
3️⃣ Enable Remote Connections
Go to SQL Server Network Configuration.
Navigate:
SQL Server Network Configuration
Protocols for InstanceName
Ensure TCP/IP is enabled.
Restart the SQL Server service after changes.
4️⃣ Check Firewall Settings
Instance Type | Port Requirement |
Default instance | TCP 1433 |
Named instance | Dynamic (must be identified manually) |
If using named instances:
Identify the assigned port.
Open the port in the firewall.
Consider configuring a static port.
5️⃣ Test Connectivity from Agent Machine
From the Liongard Agent host, run:
sqlcmd -S hostname\instance
ping hostname
nslookup hostname
or test port connectivity:
telnet hostname 1433
If DNS fails, test using IP address.
6️⃣ Verify SQL Browser Service (Named Instances Only)
Named instances require SQL Server Browser.
Requirement | Status |
SQL Browser Running | Must be ✅ |
UDP 1434 Allowed | Must be ✅ |
If disabled, the named instance will not resolve.
7️⃣ Update Liongard Agent
Ensure the Liongard Agent is up to date.
Troubleshooting Flow 🚀
Symptom | Likely Cause | Action |
Cannot locate instance | Browser service stopped | Start SQL Browser |
Works with IP but not hostname | DNS issue | Fix DNS or use IP |
Works locally but not from Agent | Firewall issue | Open required port |
Best Practices / Prevention 😉
Recommendation | Benefit |
Use static ports for named instances | Stable firewall rules |
Document ports and instance names | Faster recovery |
Avoid Browser dependency where possible | Reduced attack surface |
Keep SQL and Agent updated | Compatibility and security |
When to Contact Support 🦁
Only contact Liongard Support after completing all troubleshooting steps.
Provide the Following
Required Data | Reason |
Inspector debug logs | Shows connection failures |
| Confirms connectivity |
SQL Config screenshots | Validates services |
Firewall rules | Confirms access |
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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.