Refer to the exhibit. RTR 1 uses RTR 2 as the primary WAN exit point. When a failure occurs in the link connected to RTR 2 LAN, it takes about 40 seconds for RTR 1 to use the backup path via RTR 3…

EEM on RTR2 could script a reaction to a local event, but RTR2 is on the failing path and EEM does not independently accelerate failure detection on RTR1.

OSPF throttling timers control SPF recalculation rate, not the hello or dead interval timers used for neighbor failure detection.

BFD (Bidirectional Forwarding Detection) is a lightweight hello protocol that operates independently of OSPF and can detect link failures in milliseconds (as low as 50ms with aggressive timers). When configured between RTR1 and RTR2, BFD signals OSPF immediately upon detecting the failure, triggering a reroute via RTR3 well under 1 second.

BFD between RTR2 and RTR3 would accelerate detection on that segment, but it does not help RTR1 detect the failure of the link connecting it to RTR2.

OSPF fast hello packets (sub-second hello intervals using the 'ip ospf dead-interval minimal hello-multiplier' command) allow the dead timer to expire in less than 1 second, enabling OSPF itself to detect and react to the RTR2 link failure within the 1-second target.