When playing CnCNet games like Red Alert or Dune 2000 online using CrossOver on macOS, the online and single-player modes usually work fine, but LAN mode often crashes or shows errors.

This usually isn’t an issue with the game itself or network settings, but rather a missing critical dependency. CnCNet’s LAN feature uses a component based on an older version of .NET (specifically 2.0/3.5) to establish the LAN server (IrcD.Net). Simply having a newer .NET 4.x version installed in the CrossOver Bottle (the virtual environment) isn’t sufficient for this older component.

The solution is actually quite simple: just ensure that Microsoft .NET Framework 3.5 Service Pack 1 (SP1) is installed in the same CrossOver Bottle where CnCNet is running.

The steps are straightforward:

1. Open the CrossOver application and locate the Bottle where you installed CnCNet. If it’s a new setup, create a Bottle first.
2. Select the Bottle, then click the “Install Windows Software” button in the interface.
3. In the software library that appears, search for ".NET 3.5 SP1" or “Microsoft .NET Framework 3.5 SP1”.
4. Once found, select it and complete the installation process. It’s crucial to ensure it’s installed into the correct Bottle.
5. After successful installation, restart the CnCNet client. Now, try entering “LAN” mode. The previous crashes or errors about failing to start the service should be gone.

Extra Notes:

• While other parts of CnCNet or other Windows programs you run might still require .NET 4.x (like 4.8) or Visual C++ Runtimes, these are not necessary for fixing the LAN mode. The key is .NET 3.5 SP1.
• This method also applies if you’re using Wine directly or other Wine-based tools (like Whisky); the principle is the same – fulfilling the dependency on the older .NET runtime.