A shared I/O subsystem for a plurality of computer systems. The shared I/O subsystem includes a plurality of physical I/O interfaces and a plurality of virtual I/O interfaces where each of the computer systems is communicatively coupled to one or more of the virtual I/O interfaces. The shared I/O subsystem also includes a forwarding function having a forwarding table that logically arranges the shared I/O subsystem into one or more logical LAN switches. Each of the logical LAN switches communicatively couples one or more of the virtual I/O interfaces to at least one of the physical I/O interfaces. For each of the logical LAN switches, the forwarding function receives a data packet from any one from the group of the physical I/O interfaces and the virtual I/O interfaces, and directs the data packet to at least one from the group of the physical I/O interfaces and the virtual I/O interfaces. Two or more of the physical I/O interfaces may be aggregated to form a logical I/O interface by selectively altering entries in the forwarding table without reconfiguring the computer systems.