An apparatus having a corresponding method and computer program comprises network interfaces; a processor interface; a control circuit to remove the processor interface from associations between the interfaces and a domain; a classifier to assign codes to packets addressed to the processor interface, wherein the each code represents a protocol and comprises a flag; an allowance circuit to set the flag in the code for a packet when the packet comprises a protocol associated with the network interface that is the source of the packet, and to clear the flag otherwise; and an egress circuit to receive packets addressed to the processor interface, to drop the received packets having a code comprising a flag that is clear, and to transfer the received packets having a code comprising a flag that is set to the processor interface.