IGMP membership reports destination

When implementing IGMP, the version used will affect what destination multicast address will be used for IGMP - membership reports.

For IGMPv2, general membership queries are sent to the all-hosts multicast address These queries are sent by the multicast router to periodically check if there are still members in a multicast group.

Group-specific membership queries are sent to the multicast group address in response to a Leave Group message. When a host wants to leave a multicast group, it sends a Leave Group message to the all-routers multicast address The router then sends a group-specific membership query to the multicast group address to check if there are any remaining members in that group. If no other hosts respond, the router stops forwarding packets for that multicast group.

IGMPv3 will use the all-routers group multicast address at

IGMPv3 introduced some improvements over IGMPv2, including allowing hosts to specify source filters on the multicast streams they want to receive. This change in destination address for Membership Reports helps enable these improvements, as routers processing these reports now have a single address to listen for, making the management of multicast groups more efficient.