I was writing a blog for the company website today on deploying your .NET applications into Azure Kubernetes Service, I was using Windows images seen as it was .NET and came across a few issues while building the image.

While executing the Dockerfile from the docker build command, the restore step of the Dot Net SDK was taking a while to run, certainly longer than it should for a simple sample application.

After a short time, the command exited out with a network communication error, you can see the exiting error below.

The error returned was:

C:\Program Files\dotnet\sdk\3.1.301\NuGet.targets(128,5): error : Unable to load the service index for source https://api.nuget.org/v3/index.json. [C:\src\HelloWorld.csproj]
C:\Program Files\dotnet\sdk\3.1.301\NuGet.targets(128,5): error :   No such host is known. [C:\src\HelloWorld.csproj]

I added in a command to by Dockerfile to run a ping against google.com just to see if we had any network connectivity and this failed with unknown host.

I then looked at the configuration settings in the Docker Desktop GUI and found that from more testing no network based operations were working.

With that I added the code below into the Docker Engine settings and restarted the environment.

"dns": [
    "8.8.8.8"
  ]

After the restart, the build then completed as required and everything is now working as expected.