Which event corresponds to a router sending a notice-level syslog message?

A routing instance flapping (going up and down repeatedly) is a significant event that warrants immediate attention but isn't critical enough to halt operations. This aligns with the "notice" severity level (level 5) in syslog, indicating normal but significant conditions that should be noted. "A network device has restarted" typically generates a "warning" (level 4) or "informational" (level 6) message, as it's a planned or expected event. "A debug operation is running" is usually an "informational" (level 6) or "debugging" (level 7) message, as it's a user-initiated diagnostic process. "An ARP inspection has failed" is a more severe issue, often generating a "critical" (level 2) or "alert" (level 1) message, as it indicates a potential security breach or network instability.