vRtrIgmpGenRobustCount 1.3.6.1.4.1.6527.3.1.2.23.1.1.1.4

The Robustness Variable allows tuning for the expected packet loss on a subnet. If a subnet is expected to be lossy, the Robustness Variable may be increased. IGMP is robust to (Robustness Variable-1) packet losses.