Testing forwarding states of a network device using probe detection and reflection

Abstract

A deterministic model is described that is used for testing networks by exercising forwarding rules (e.g., layer 2 and layer 3) on network devices. Probe detection on a peer network device B can be implemented using a global register available to all input pipelines. The global register can be used to check a source and destination port in a User Datagram Protocol (UDP) header. If there is a match, the packet is considered a probe, and a probe detection signal is transmitted to an output pipeline to redirect the probe back to the input port. Network device A can then capture the reflected probe using layer 2 hardware and redirect it to the CPU in order to verify the actual forwarding behavior applied on the probe packet. In an alternative embodiment, probe detection logic can be incorporated in an ACL at a beginning of a pipeline for switching packets.