Home > SQL, Uncategorized > Error: 26 – Error Locating Server/Instance Specified

Error: 26 – Error Locating Server/Instance Specified

One of my devs stopped by my desk late yesterday afternoon with an issue.  He had just received a new workstation and was running through getting SSMS configured to his liking.  As he registered SQL Servers he got the following error when attempting to connect to one of my cluster nodes:


Cannot connect to SQL1\Instance1.



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) (Microsoft SQL Server, Error: -1)

Now, my first instinct was that he had a typo in the instance name so I sent him back to his desk to verify the spelling and try again.   

If only it had been that simple!   I suppose I should also share that I knew full well that this instance was up and running just fine – I and about 150 other folks were connected to it with no issues.  He was also able to connect to every other sql instance he had attempted to connect to with SSMS 2008R2 with no issue. 

My next step was to verify that he had the SQL Native client installed, and that TCP was enabled because that is the only protocol enabled on the suspect SQL instance.  As I’m sure you can guess SNC was just fine, and did indeed have TCP enabled.  He could also ping the server hosting the suspect SQL instance.

After digging a bit on the web I found this blog from the SQL Protocols team with some steps to follow for trouble shooting this very issue.  As I read through it I realized that I had already checked everything on the list of steps and I was still seeing the issue.  Just as I was getting ready to search again I saw this little paragraph:

There is one corner case where you may still fail after you checked step 1)-4). It happens when a) your server is a named instance on cluster or on a multi-homed machine, and b) your client is a Vista machine with Firewall on. I have explained the details at: Unable to connect to a SQL Server named instance on a cluster


Ah ha!  My dev was running Windows 7, not Vista, but still – the firewall is on by default and pretty likely that it was left on.   A quick call to him to walk him through disabling the firewall and he was up and running.   

The only thing left to do is have our PC team update their documentation to include disabling Windows Firewall as part of the profile setup on new deployments.

Categories: SQL, Uncategorized
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