How often does a router issue IGMP Host Membership Reports for group 224.0.0.2?

According to the Internet Group Management Protocol (IGMP) standard, network devices have distinct roles. Routers function as "Queriers," responsible for sending IGMP Membership Queries to discover which multicast groups have active members on their attached networks. End-hosts (or receivers) are responsible for sending IGMP Host Membership Reports to signal their interest in joining or remaining in a multicast group.

A router, by protocol definition, does not issue Host Membership Reports. Therefore, a router will never issue a report for any group, including the well-known "All Routers" multicast address 224.0.0.2. This address is used for communication between multicast routers (e.g., for PIM hellos), not for a router to join a group as a host.

B, C, D, E: These options are incorrect because they suggest a specific time interval for an event—a router issuing a Host Membership Report—that fundamentally does not occur as per the IGMP specification.

1. Nokia 7750 SR OS Multicast Protocols Guide, Release 21.10.R1: In the "IGMP" chapter, the section "IGMP Overview" states, "IGMP is used by IP hosts to report their multicast group memberships to any immediately connected multicast router... Multicast routers use IGMP to learn, for each of their attached physical networks, which groups have members." This document consistently defines routers as receivers of reports, not senders.

2. IETF RFC 2236 - Internet Group Management Protocol, Version 2: Section 2, "Protocol Description," explicitly defines the roles: "Hosts send Membership Reports to report their group memberships, and routers send Membership Queries to discover which groups have members on their attached networks." This foundational RFC confirms that routers do not send reports.

3. IETF RFC 3376 - Internet Group Management Protocol, Version 3: Section 3, "Protocol Description," reinforces this role separation: "IGMP is an asymmetric protocol. The behavior of a host is different from the behavior of a router... Routers use IGMP to learn which multicast addresses are of interest to the hosts attached to their local network." This confirms the behavior is consistent in the newer version of the protocol.