The answer is that a host at 192.168.1.100 has joined group 239.2.2.2. This is correct because the "show ip igmp groups" output interpretation reveals that the "Last Reporter" field identifies the most recent host to send an IGMP membership report for that multicast group on the subnet. The "Uptime" of 1 day and 4 hours confirms the group has been active, while the "Expires" timer of 00:02:10 indicates the router is still receiving reports, meaning at least one active listener exists. On the ENCOR 350-401 exam, this command tests your ability to read IGMP state information and distinguish between a host that has joined versus a router that is simply forwarding traffic—a common trap is assuming the "Last Reporter" is the source of the multicast stream. Remember the memory tip: "Last Reporter = Last Listener," not the sender.
350-401 IP Multicast Practice Question
This 350-401 practice question tests your understanding of ip multicast. Examine the command output carefully: the correct answer depends on what the output actually shows, not on general recall alone. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A network engineer executes the following command on Router R3:
R3# show ip igmp groups 239.2.2.2
IGMP Connected Group Membership
Group Address Interface Uptime Expires Last Reporter
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
A host at 192.168.1.100 has joined group 239.2.2.2.
The 'show ip igmp groups' output shows that group 239.2.2.2 is present on interface GigabitEthernet0/0, with the last reporter being 192.168.1.100. The uptime is 1 day and 4 hours, and the expiry timer is about 2 minutes. This indicates that there is at least one IGMP host on that subnet interested in the group. The correct answer is that a host at 192.168.1.100 has sent an IGMP report for this group.
Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
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 is the host that last sent an IGMP report, not necessarily the source.
✓
A host at 192.168.1.100 has joined group 239.2.2.2.
Why this is correct
The last reporter indicates the host that sent the most recent IGMP membership report for this group.
The output does not indicate IGMP version; it only shows group membership.
Common exam traps
Common exam trap: usable hosts are not the same as total addresses
Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.
Trap categories for this question
Command / output trap
The output does not show RP information.
Detailed technical explanation
How to think about this question
Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.
KKey Concepts to Remember
CIDR notation defines the prefix length.
Block size helps identify subnet boundaries.
Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
The required host count determines the smallest suitable subnet.
TExam Day Tips
→Write the block size before choosing the subnet.
→Check whether the question asks for hosts, subnets or a specific address range.
→Do not confuse /24, /25, /26 and /27 host counts.
Key takeaway
Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Real-world example
How this comes up in practice
A network engineer segments a warehouse floor into three subnets: 20 scanners, 5 printers, and 2 management hosts. Picking the wrong mask wastes addresses or leaves too few usable hosts. Exam questions test whether you can apply CIDR notation, calculate block size, and identify the correct usable-host range for a given prefix.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 350-401 question in full detail.
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related 350-401 subnetting questions on CIDR, address ranges, and subnet selection.
IP Multicast — This question tests IP Multicast — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: A host at 192.168.1.100 has joined group 239.2.2.2. — The 'show ip igmp groups' output shows that group 239.2.2.2 is present on interface GigabitEthernet0/0, with the last reporter being 192.168.1.100. The uptime is 1 day and 4 hours, and the expiry timer is about 2 minutes. This indicates that there is at least one IGMP host on that subnet interested in the group. The correct answer is that a host at 192.168.1.100 has sent an IGMP report for this group.
What should I do if I get this 350-401 question wrong?
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related 350-401 subnetting questions on CIDR, address ranges, and subnet selection.
What is the key concept behind this question?
CIDR notation defines the prefix length.
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Question Discussion
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