A system for supporting a flooding mechanism in a middleware machine environment operating on one or more microprocessors, comprising: a gateway instance, wherein the gateway instance is associated with an external port that is adapted to receive one or more data packets from an external network; one or more host servers (104, 105, 106, 107) on which a plurality of virtual interfaces (121...128) are provided, wherein each said host server is associated with one or more virtual machines (131...140) that operate to process the one or more data packets, wherein at least one virtual interface is a parent virtual interface that is associated with one or more child virtual interfaces, and wherein policy information associated with the parent virtual interface on the gateway instance limits addresses and/or identifications that the one or more child virtual interfaces can be associated with; wherein at least one packet is specified with an unknown destination address when it is received at the external port of the gateway instance, and wherein the gateway instance operates to send said at least one packet to: (i) a multicast group, wherein the multicast group operates to forward the at least one packet to one or more said host servers in the multicast group; or (ii) a designated virtual interface on a host server that is associated with a packet process proxy, wherein the packet process proxy on the host server operates to forward the at least one packet to a target virtual machine to process the at least one packet. a gateway instance, wherein the gateway instance is associated with an external port that is adapted to receive one or more data packets from an external network; one or more host servers (104, 105, 106, 107) on which a plurality of virtual interfaces (121...128) are provided, wherein each said host server is associated with one or more virtual machines (131...140) that operate to process the one or more data packets, wherein at least one virtual interface is a parent virtual interface that is associated with one or more child virtual interfaces, and wherein policy information associated with the parent virtual interface on the gateway instance limits addresses and/or identifications that the one or more child virtual interfaces can be associated with; wherein at least one packet is specified with an unknown destination address when it is received at the external port of the gateway instance, and wherein the gateway instance operates to send said at least one packet to: (i) a multicast group, wherein the multicast group operates to forward the at least one packet to one or more said host servers in the multicast group; or (ii) a designated virtual interface on a host server that is associated with a packet process proxy, wherein the packet process proxy on the host server operates to forward the at least one packet to a target virtual machine to process the at least one packet. (i) a multicast group, wherein the multicast group operates to forward the at least one packet to one or more said host servers in the multicast group; or (ii) a designated virtual interface on a host server that is associated with a packet process proxy, wherein the packet process proxy on the host server operates to forward the at least one packet to a target virtual machine to process the at least one packet.