This read-write object sets the lifetime, in minutes, that a dynamically learned ARP entry remains valid in the device's ARP table before being aged out. Admins tune it to balance ARP table freshness against control-plane overhead, since a shorter lifetime reacts faster to MAC address changes but generates more ARP re-resolution traffic. Lowering rcArpExtLifeTime to 5 minutes would make the switch re-verify neighbor MAC addresses more frequently, useful in an environment where hosts change NICs or move between ports often.