350-401 Practice Question: Executes the following command on Router R3: R3#…

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

• ✗

  The multicast group is being sourced from 192.168.1.100.

  Why it's wrong here

  The “last reporter” field in IGMP group output identifies the host that most recently sent an IGMP membership report for the group, not the source of the multicast stream. A multicast source is the device that sends data to the group address, and it does not need to be a member of the group or send IGMP reports. The router uses IGMP to track interested receivers on its directly connected networks, while source information is handled by routing protocols like PIM or by the multicast stream itself. Therefore, 192.168.1.100 is the last host to report membership, not the source.

• ✓

  A host at 192.168.1.100 has joined group 239.2.2.2.

  Why this is correct

  The correct interpretation is that a host with IP address 192.168.1.100 has joined multicast group 239.2.2.2. In the output of “show ip igmp groups” or “show ip igmp group <group>”, the “Last Reporter” field shows the IP address of the host that sent the most recent IGMP Membership Report for that group on that interface. Since the host has sent that report, the router knows to forward multicast traffic destined for 239.2.2.2 to the interface, and the host is an active receiver. This is precisely what the command output is indicating.

• ✗

  The router is the RP for this group.

  Why it's wrong here

  This output from IGMP group membership commands does not contain any rendezvous point (RP) information. RP mappings are displayed by PIM-specific commands such as “show ip pim rp mapping” or “show ip pim rp-hash”, and they define the router that acts as the meeting point for multicast traffic in PIM sparse mode. The router’s RP role is a PIM configuration detail, not an IGMP group membership detail. Moreover, the RP is a router identifier, and this output shows the IP address of a host that sent an IGMP report, so it cannot be interpreted as indicating that the router itself is the RP.

• ✗

  The group is using IGMP version 3.

  Why it's wrong here

  The output only displays group membership state, specifically the group address, interface, and last reporter; it does not reveal the IGMP version in use. IGMP version is negotiated and configured per interface and can be verified with “show ip igmp interface”, which shows the version and querier state. While a “last reporter” field exists in IGMPv2 and IGMPv3, its presence alone does not identify the version. Since the command output lacks any version indication, claiming the group uses IGMPv3 is unsupported and incorrect.