US Patent 11563668 Network devices using probes to test forwarding rules

A network switch having hardware thereon for transmitting probes to neighbor devices for exercising forwarding states (e.g., layer 2 and layer 3) on the switch. A light-weight agent resides on one or both of neighbor network devices and can be used to control the testing. Probe allocation can be managed locally on a source device based on a layer 3 routing table. One or more probes originating from the source network device (device A) from a local CPU are routed on the same network device A in hardware and sent out on a link towards a peer device (device B). Peer device B captures the probe using an Access Control List (ACL) hardware, and reflects the probe back to network device A on the ingress port. Network device A can then capture the reflected probe using ACL hardware and verifies the actual forwarding behavior applied on the probe packet.