title: “No such host” when Azure web app attempts to communicate with Azure database
body: <p>Now, I have both my App Service and Database deployed in Azure, they are fine. I can browse to the site perfectly and it all seems to function.</p>
  
  <p>Similarly, I've added a firewall rule in Azure to enable me to connect to the database server and query the database from my local SQL Server Management Studio.</p>
  
  <p>Additionally, when I change my local web application (on my Local IIS Express server) to point to the Azure database it also works fine.</p>
  
  <p>However, when I deploy the application I keep getting: <strong>"No such host is known"</strong>:</p>
  
  <blockquote>
    <p>[SqlException (0x80131904): 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: TCP Provider, error: 0 - No such host is
    known.)] I've tried adding the IP address of the App Service to the
    database server. I've even tried white listing the entire IP address
    range just to completely discount that and it doesn't work either!</p>
  </blockquote>
  
  <p>Any ideas?</p>