Connection to remote SQL server breaks when upgrading web server to .net framework 4.6.1

Question

We\'re currently working on updating our asp.net web application (hosted on IIS 7.5) from .net framework v4.5 to v4.6.1. On small lower environments/local development in which S

Answer 1

Update - so it looks like we've found (at the least the solution to) the problem. Turns out -- as the exception suggested -- that by increasing the connection timeout property on our connection string (default is 15 seconds, we set it to 60 seconds), we were able to make a connection to our database through our web app. However, opening this connection takes a prohibitively long time, so we started looking for solutions to make our connection open faster. We've discovered that we have Netbios over TCP/IP enabled on our database server, and that by opening up UDP ports (137, 138) on our network for Netbios access, we were able to open connections to the database way faster, timing at <1 second instead of >15 seconds. We're still not sure why the .net upgrade exposed this problem. By testing with a UDL file, we were able to establish that the network connectivity to our database performs about the same on our web servers on .net 4.5 as on our web servers on .net 4.6.1. So it seems as if our connections were opening so slowly that we were already very close to timing out, and some sort of extra logic/cruft in 4.6.1 put us over the edge. I'll update if we find more clarity on that.