Application server suddenly cannot reach SQL Server: error 40, could not open a connection. Sometimes we also see Network Interfaces error 26 or a login failed. SSMS on the database box itself connects fine. Checklist?
Fix Named Pipes Provider error 40 in SQL Server
Solved SQL & Databases
AJ
Andrew Jackson May 21, 2019
2 replies
10,650 views
Reviewed by moderators
Local works, remote fails is the signature of a network path issue, not the database. Down the list:
1
SQL Server Configuration Manager: enable TCP/IP under network protocols, restart the SQL service. Disabled TCP is the number one cause.
2
Named instance: the SQL Browser service must be running or connections need the explicit port. Error 26 specifically means the browser lookup failed.
3
Firewall: inbound rule for TCP 1433 plus UDP 1434 for the browser.
4
Only after connecting, a login failed message is a real credentials or permissions issue. Check the mapped user and default database.
TCP/IP was disabled after someone reinstalled the instance. One checkbox, one restart. Solved.