The switch hardware can route traffic based on information stored in hardware and software routing tables. Routing tasks are completed much faster when the routes are already stored in hardware routing tables. When packets are routed using the hardware routing tables, this is called fast-path routing, because the packets take the fast path through the switch.
The switch hardware provides the fast path, and the ExtremeXOS software provides the routing management capabilities, including management of the hardware routing tables. The software collects all routing information, manages the routes according to the switch configuration, and stores the appropriate routes in the hardware routing tables. When an IP unicast packet arrives and the destination IP address is not found in the hardware route tables, it is routed by software. The software processing takes more time than the fast path, so routing based on the software tables is called slow-path routing.