A PCI-Express module that is coupled to plural host systems and to at least an input/output (I/O) device is provided. The PCI-Express module includes an upstream port module and a downstream port module that use a mapping table to facilitate the plural host systems sharing the I/O device by modifying a transaction layer packet (TLP) field. For upstream ID based traffic, a source identifier is replaced based on the mapping table and a destination identifier is replaced with a value that is captured during upstream port module initialization. For upstream address based traffic, the mapping table routes TLPs by using a downstream port number and a function number in a source identification field. For downstream ID based traffic, a destination identifier is replaced by using the mapping table for routing TLPs. For downstream address based traffic, the PCI-Express module uses an address map to route TLPs.