file: /proc/sys/net/ipv4/conf/interface/app_solicit
variable: net.ipv4.conf.interface.app_solicit
Official reference

The maximum number of probes to send to the user space ARP daemon via netlink before dropping back to multicast probes (see mcast_resolicit). Defaults to 0.

Nb: per interface setting (where “interface” is the name of your network interface); “all” is a special interface: changes the settings for all interfaces.