A cross-network bridging apparatus includes a bus interface and bridging circuitry. The bus interface is configured for connecting to a system bus. The bridging circuitry is configured to translate between (i) system-bus transactions that are exchanged between one or more local devices that are coupled to the system bus and served by the system bus and one or more remote processors located across a network from the apparatus, and (ii) data units that convey the system-bus transactions, for transmitting and receiving as network packets over the network to and from the remote processors.