I'm using onEnter in some Route elements that require authentication. On client-side things just worked; when rendered on server I got exceptions. As it turned out I was trying to access login-related info in the redux store in the function called by onEnter and it wasn't configured yet by boot-server.tsx. A simple issue to correct once I found it. To help other poor souls it might be a good idea to move the configureStore() call before the match in the template so client and server-side work the same.

https://github.com/aspnet/JavaScriptServices/blob/dev/templates/ReactReduxSpa/ClientApp/boot-server.tsx