A PCIe Fabric comprising: a first processor connected to a first slice of a plurality of slices of the PCIe fabric and a second processor connected to a second slice of the plurality of slices; an Input/Output, I/O, tier comprising a first IO tier switch in the first slice and a second IO tier switch in the second slice; a hub tier comprising a plurality of hub tier switches, wherein the plurality of hub tier switches comprises a first hub tier switch in the first slice and a second hub tier switch in the second slice, wherein the first IO tier switch is connected via a first downstream port to the second hub tier switch using a crosslink; wherein the first IO tier switch is configured to: receive, from a client, at a second downstream port, a transaction layer packet, TLP; make a first determination that an address in the TLP is not associated with any multicast address range in the first IO tier switch; make a second determination that the address in TLP is not associated with any downstream port in the first IO tier switch; based on the first and second determinations, route the TLP to the first hub tier switch using a first upstream port on the first IO tier switch; wherein the first hub tier switch is configured to: receive, from the first IO tier switch, the TLP at a third downstream port; make a third determination that the TLP is associated with a first multicast group; based on the third determination: generate a first rewritten TLP that is a copy of the received TLP and comprises a new address associated to a first target device and route the first rewritten TLP to the first target device via a fourth downstream port on the first hub tier switch, wherein the fourth downstream port is a subscriber of the first multicast group. a first processor connected to a first slice of a plurality of slices of the PCIe fabric and a second processor connected to a second slice of the plurality of slices; an Input/Output, I/O, tier comprising a first IO tier switch in the first slice and a second IO tier switch in the second slice; a hub tier comprising a plurality of hub tier switches, wherein the plurality of hub tier switches comprises a first hub tier switch in the first slice and a second hub tier switch in the second slice, wherein the first IO tier switch is connected via a first downstream port to the second hub tier switch using a crosslink; wherein the first IO tier switch is configured to: receive, from a client, at a second downstream port, a transaction layer packet, TLP; make a first determination that an address in the TLP is not associated with any multicast address range in the first IO tier switch; make a second determination that the address in TLP is not associated with any downstream port in the first IO tier switch; based on the first and second determinations, route the TLP to the first hub tier switch using a first upstream port on the first IO tier switch; receive, from a client, at a second downstream port, a transaction layer packet, TLP; make a first determination that an address in the TLP is not associated with any multicast address range in the first IO tier switch; make a second determination that the address in TLP is not associated with any downstream port in the first IO tier switch; based on the first and second determinations, route the TLP to the first hub tier switch using a first upstream port on the first IO tier switch; wherein the first hub tier switch is configured to: receive, from the first IO tier switch, the TLP at a third downstream port; make a third determination that the TLP is associated with a first multicast group; based on the third determination: generate a first rewritten TLP that is a copy of the received TLP and comprises a new address associated to a first target device and route the first rewritten TLP to the first target device via a fourth downstream port on the first hub tier switch, wherein the fourth downstream port is a subscriber of the first multicast group. receive, from the first IO tier switch, the TLP at a third downstream port; make a third determination that the TLP is associated with a first multicast group; based on the third determination: generate a first rewritten TLP that is a copy of the received TLP and comprises a new address associated to a first target device and route the first rewritten TLP to the first target device via a fourth downstream port on the first hub tier switch, wherein the fourth downstream port is a subscriber of the first multicast group.