Monthly Archives: January 2015

Reasons you can’t connect to SQL Server

“I can’t connect, can you look at the logs?”

Nope, not today, this is not how we do this. How is the server to LOG if it never receives the request? Do you think the server somehow magically anticipated that you wanted to run a query for the first time? What server are you even talking about???

Connection errors are generally logged on the client side. First read the message carefully and thoroughly for best results. The majority of common errors can be broken down into three categories:

Client issue
Network issue
Server issue

The nature of the word “Connection” means there is some fuzzy areas where two of the three CNS creatures rub uglies. There is a network adapter on the client and a network adapter on the server, and well.. there is a network.

Lets look at one of my more popular reasons you can’t connect to SQL Server, Login Failed.

So which is that, C… N… or S? I can pretty much rule out the network since the client received a message from the server. Maybe it is not even an issue at all, it is a feature I implemented to prevent you from logging into a production server. I really want to put it in the server category, but as I look back on actual cases, it is mostly the fact that access was never requested until it didn’t work. So that is a layer 8 issue with the planning protocol.

Long story short, I really wanted to categorize this list and also provide solutions but it really depends on the situation of the error. Hopefully, this list doesn’t grow much more since I have gotten better at anticipating people who may eventually want to connect to my databases. Without any further complaints, here are the reasons off the top of my head that you can’t connect to SQL Server:

1. You don’t have login access
2. Your login doesn’t have connect privileges
3. The Windows firewall is blocking you
4. The network firewall is blocking you
5. The login doesn’t have public access to the database
6. The server is out of memory
7. The server is actually down
8. The database is in single_user mode
9. The service account is locked out
10. SQL Authentication isn’t enabled on the server
11. You are trying SQL Auth when you should be using Windows Integrated
12. You are typing the password wrong
13. The login is locked out
14. The login is disabled
15. Server cannot generate the SSPI context
16. The service was started with option -m (single user)
17. The vmware host doesn’t have the correct vlan defined
18. The SQL Server’s ip configuration is wrong
19. The network switch doesn’t allow the vlan on that port
20. The distributed switch doesn’t have LACP enabled on that port group
21. The SQL Service is being updated
22. The Windows server is being updated
23. You are not specifying the non-standard port
24. You have the wrong instance name
25. You have the wrong server name
26. You have the wrong port
27. You communicated the wrong port to the network firewall admin
28. You are using the :port syntax instead of the ,port syntax
29. SQL is not set to listen on TCP/IP
30. You ran the C: drive out of space causing a cascading failure
31. You are not connected to the VPN
32. You are connected to the guest wifi
33. You bumped the wifi switch on your laptop

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Posted by on January 21, 2015 in SQL Admin, SQL Dev