A flattening portal bridge (FPB) is provided to support addressing according to a first addressing scheme and a second, alternative addressing scheme. The FPB comprises a primary side and a secondary side, the primary side connects to a first set of devices addressed according to a first addressing scheme, and the secondary side connects to a second set of devices addressed according to a second addressing scheme. The first addressing scheme uses a unique bus number within a Bus/Device/Function (BDF) address space for each device in the first set of devices, and the second bus addressing scheme uses a unique bus-device number for each device in the second set of devices.