I have two instances running on Amazon AWS EC2. One is running MSSQL Server 2005, the other is running a web application. I CAN connect to the database in my app using a connection string that references the Public IP of my EC2 instance running SQL Server. I CANNOT connect from the web app server if I change the connection string to reference the database servers Private IP Address. But I can connect if I run that same code on the database server itself. I can remote desktop from the app server to the database server using the private IP. I have a feeling there is something in my SQL Sever configuration that is preventing this remote connection. I have remote connections enabled, I have it set to listen on all IP addresses. Any ideas? Other things I've done: - Added exceptions to Windows Firewall - Tried connecting to using EC2 DNS Names