To overcome scalability and control overhead problems existing in inter-domain multicast, DINloop (Data-In-Network loop) based multicast with MPLS is proposed. DINloop is a special logical path formed using MPLS Label Switched Paths and it consists of multiple DIN Nodes which are core routers that connect to each intra-domain. We use DINloop to manage inter-domain multicast group membership. Facilitated by the DINloop, multiple DIN Nodes in the core network easily form a Steiner tree for multicast traffic. Furthermore, traffic for different multicast groups sharing the same path are aggregated through a label stack. Simulations demonstrate that DINloop-based multicast results in less message load needed to form the multicast structure. In addition, the routing table size in other core routers does not increase as the number of multicast group increases, and therefore routing scalability is improved. Finally, the inter-domain multicast delay in DINloop-based multicast is lower than that of a unidirectional tree.