You can configure the IGS switch as a querier for a specific VLAN. You can also configure the group-specific query interval for that VLAN. The IGS switch stops acting as a querier on the reception of general queries. The switch resumes the querier function when there are no IGMP routers in the network. The IGS switch continues to act as a querier on the reception of router control messages (for instance, PIM or OSPF messages), and the switch acts as a querier when the router port is operationally down and there are no router ports in the switch. Before you can configure IGS features, you must configure your network environment, as described in Topology Example.