A shared I/O subsystem that couples a plurality of computer systems to at least one shared I/O interface. The shared I/O subsystem includes a plurality of virtual I/O interfaces that are communicatively coupled to the computer systems. Each of the computer systems includes a virtual adapter that communicates with one of the virtual I/O interfaces. The shared I/O subsystem further includes a forwarding function having a forwarding table. The forwarding table includes a plurality of entries corresponding to each of the virtual I/O interfaces. The forwarding function receives a first I/O packet from one of the virtual I/O interfaces and uses the forwarding table to direct the first I/O packet to at least one of a physical adapter associated with the at least one shared I/O interface and one or more of other ones of the virtual I/O interfaces. The forwarding function also receives a second I/O packet from the physical adapter and uses the forwarding table to direct the second I/O packet to one or more of the virtual I/O interfaces.