The current inter-domain routing in the Internet, which is based on BGP-4, does not allow for the use of multiple paths, but rather restricts the routing to a single path for each destination prefix. This fact is especially unfortunate considering the vast route diversity which is inherently present in the global Internet graph. Therefore, we propose Inter-Domain Route Diversity (IDRD) as an overlay mechanism which enables efficient, backwards compatible and incrementally deployable introduction of route diversity in the Internet. Beyond presenting the architecture of IDRD, this paper also presents the conditions which ensure the stability of the proposed mechanism as a fundamental prerequisite for its deployment in real-world scenarios.