Error route
A special route called errorRoute is registered that will match when the route doesn't match (exact or partial) any route in the routing configuration. You can use this route to render a widget to inform the user that the route does not exist.
import { create, tsx } from '@dojo/framework/core/vdom';
import Route from '@dojo/framework/routing/Route';
const factory = create();
export default factory(function App() {
    return (
        <div>
            <Route
                id="errorRoute"
                renderer={() => {
                    return <div>Unknown Page</div>;
                }}
            />
        </div>
    );
});
If there is a default route registered, this will take precedence over the error route on the initial application load.