Routing between multiple hosts and adapters in a PCI environment is provided by a method and system. A Destination Identification (DID) field is inserted in a field of the PCI bus address (PBA) of transaction packets dispatched through PCI switches. A particular DID is associated with a particular host or system image, and thus identifies the physical or virtual end point of the packets. The method and system may track connections such that when particular host of a root node becomes connected to a specified switch, a PCI Configuration Master (PCM), residing in one of the root nodes, is operated to enter a destination identifier or DID into a table. The DID is then inserted in the PBA of packets directed through the specified switch from the particular host to one of the adapters.