This read-create value is the IGMP Robustness Variable for the interface, tuning tolerance for expected packet loss on the subnet, defaulting to 2. Increasing it makes IGMP more resilient to lossy links by allowing one fewer than the Robustness Variable's worth of consecutive packet losses without falsely declaring a group membership lost, at the cost of somewhat slower convergence. For example, on a subnet with known Wi-Fi packet loss, an admin might raise igmpInterfaceRobustness from the default of 2 to 3 or 4 to reduce false membership timeouts.