While SNMP OID polling (Option B) could theoretically detect interface state, the most direct, low- latency, and idiomatic EEM approach is subscribing to syslog pattern matching (`event syslog pattern`), since interface up/down events naturally generate a standard `%LINK-3-UPDOWN` syslog message that EEM can capture in real time and trigger an action on (e.g., `action cli command` to invoke a Python or Bash-shell script). `event timer` is periodic, not event-driven;
`event none` is only for manually-triggered applets. This tests practical judgment in selecting the correct EEM event detector.