US Patent 9270592 Hash collision avoidance in network routing

Network device and method for routing a packet and setting up a new flow. The device includes a packet classifier, a field-selection table, a hash module, and a routing table. A packet is routed by finding an entry in the field-selection table using the packet classifier, selecting bits from the packet based on the entry in the field-selection table, and hashing the selected bits along with an identifier from the packet classifier or the field-selection table, using the hash module. The hash result is used to locate instructions in the routing table. When setting up a new flow, the hash module result may point to an existing entry in the routing table. In such instances, a new entry is added to the packet classifier, such that the hash module will produce a different result that points to an available entry in the routing table.