This enables IGMP tuning on a lossy network if a switch is the querier. On such a network it may be increased. It is set stack-wide. The default value is 1. The range is 1 to 2. There could be a Low(1) or High(2) setting. It is used to derive a timeout interval. If no IGMP v2 queries are heard on this VLAN within this timeout interval, the local switch will take over the querier role in the VLAN, assuming the switch has no router ports: Other Switch Querier Present Interval = (Robustness x General Query Interval) + 1/2(General Max Query-Response Interval) = 65 seconds by default The Robustness is also used to derive another interval. The amount of time that must pass before the querying switch decides that there are no more hosts listening to a particular multicast in seconds: Group Membership Interval = (Robustness x General Query Interval) + General Max Query-Response Interval = 70 seconds by default.