Q & A on Multi-homed host network bandwidth Q: Can a multi-homed host obtain a higher aggregate bandwidth if set up on two separate subnets, yet within the same autonomous system? My position is that an ISA bus wouldn't make effective use out of two 10 M-bit NICs (excess capacity) and that the network operating system would have to be intelligent enough to know that LANA and LANB were effectively the same network. A: There are two issues. First, there's the addressing/routing problem -- a multihomed host has two (or more) IP addresses, one for each network connection. Because a given remote host must choose one address when its ends packets, all packets arriving from that host are routed to one interface (i.e., there is no load-balancing for incoming packets from a specific source). Similarly, all outgoing packets for a specific destination are routed over one path, meaning that they leave from a single interface.Although it's possible to arrange two parallel networks and send half the packets over each, few systems use such an arrangement (the technical term for such an arrangement is *network striping*). So, I assume you refer to the more common multihomed situation in which simultaneous transfers on each interface arise because the computer is communicating with multiple computers concurrently (e.g., a server that simultaneously communicates with multiple clients, some of which are reachable over one network while others are reachable over another network).If we assume equal volumes of traffic from each interface, we can imagine that both are fully loaded. In such cases, the question you pose is valid:where is the bottleneck in the system? It could be the processor, the memory (in particular, the DMA speed), the interrupt overhead, the operating system, the bus, the network interface card, or the network media access. For example, two 100Base-T cards can saturate most slow buses. As for 10Base-T, the actual bus utilization needs to account for the minimum inter-packet gap as well as the header and trailer on each frame.