title: Azure.RequestFailedException: No such host is known
body: <p>I have an application (aspnet core app 3.1) where I load data during startup from azure blob storage with the following code:</p>
  
  <pre><code>BlobClient client = new BlobClient(loaderOptions.ConnectionString, loaderOptions.BlobContainerName, loaderOptions.BlobName);
  
  var response = client.Download();
  
  using (var memoryStream = new MemoryStream())
  {
       response.Value.Content.CopyTo(memoryStream);
       return memoryStream.ToArray();
  }
  </code></pre>
  
  <p>Locally, on my PC everything works fine. But when I publish this app to azure app service (windows) I get the following errors:</p>
  
  <pre><code>Unhandled exception. System.AggregateException: Retry failed after 6 tries. (No such host is known.) (No such host is known.) (No such host is known.) (No such host is known.) (No such host is known.) (No such host is known.)
  
   ---&gt; Azure.RequestFailedException: No such host is known.
  
   ---&gt; System.Net.Http.HttpRequestException: No such host is known.
  
   ---&gt; System.Net.Sockets.SocketException (11001): No such host is known.
  
     at System.Net.Http.ConnectHelper.ConnectAsync(String host, Int32 port, CancellationToken cancellationToken)
  
     --- End of inner exception stack trace ---
  
     at System.Net.Http.ConnectHelper.ConnectAsync(String host, Int32 port, CancellationToken cancellationToken)
  
     at System.Net.Http.HttpConnectionPool.ConnectAsync(HttpRequestMessage request, Boolean allowHttp2, CancellationToken cancellationToken)
  
     at System.Net.Http.HttpConnectionPool.CreateHttp11ConnectionAsync(HttpRequestMessage request, CancellationToken cancellationToken)
  
     at System.Net.Http.HttpConnectionPool.GetHttpConnectionAsync(HttpRequestMessage request, CancellationToken cancellationToken)
  
     at System.Net.Http.HttpConnectionPool.SendWithRetryAsync(HttpRequestMessage request, Boolean doRequestAuth, CancellationToken cancellationToken)
  
     at System.Net.Http.RedirectHandler.SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
  
     at System.Net.Http.HttpClient.FinishSendAsyncUnbuffered(Task`1 sendTask, HttpRequestMessage request, CancellationTokenSource cts, Boolean disposeCts)
  
     at Azure.Core.Pipeline.HttpClientTransport.ProcessAsync(HttpMessage message)
  
     --- End of inner exception stack trace ---
  </code></pre>
  
  <p>A week ago everything worked fine. Now I have created new service plans and storage accounts (deleted old ones) and come across this problem.</p>
  
  <p>What can be solution?</p>
  
  <p><a href="https://i.stack.imgur.com/CMi6t.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/CMi6t.png" alt="enter image description here"></a></p>