router_probe_interval

file: /proc/sys/net/ipv6/conf/interface/router_probe_interval
variable: net.ipv6.conf.interface.router_probe_interval
Official reference

Minimum interval (in seconds) between Router Probing described in RFC4191.

Default: 60

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

source