- A
IGMP snooping reduces multicast flooding on a VLAN by forwarding traffic only to ports that have joined the group.
Correct because IGMP snooping examines IGMP join messages and builds a forwarding table so multicast frames are sent only to interested receivers.
- B
IGMP snooping builds a Layer 2 forwarding table that maps multicast MAC addresses to switch ports.
Correct because the snooping switch records which ports have active members for each multicast group, using the multicast MAC address derived from the IP group address.
- C
IGMP snooping forwards IGMP membership reports only toward the multicast router (querier).
Correct because the switch forwards IGMP reports only out of the port where the querier (multicast router) is connected, preventing unnecessary flooding to other hosts.
- D
IGMP snooping suppresses all IGMP general queries from the multicast router.
Why wrong: Incorrect because IGMP snooping does not suppress queries; it forwards them to all ports in the VLAN so hosts can respond. Queries are only suppressed in IGMP proxy reporting, which is a different feature.
- E
IGMP snooping requires PIM to be enabled on the switch.
Why wrong: Incorrect because IGMP snooping operates at Layer 2 and does not require PIM; it is independent of Layer 3 multicast routing protocols.
350-401 IP Multicast Practice Question
This 350-401 practice question tests your understanding of ip multicast. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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.
Which three statements about IGMP snooping are true? (Choose three.)
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
IGMP snooping reduces multicast flooding on a VLAN by forwarding traffic only to ports that have joined the group.
IGMP snooping optimizes multicast forwarding at Layer 2 by monitoring IGMP messages. It builds a snooping table, forwards reports only to the querier, and can be configured with static entries. It does not suppress queries or require PIM.
Key principle: A trunk being up does not mean the VLAN is allowed across it. Always verify the allowed VLAN list and whether the VLAN exists on both switches.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
IGMP snooping reduces multicast flooding on a VLAN by forwarding traffic only to ports that have joined the group.
Why this is correct
Correct because IGMP snooping examines IGMP join messages and builds a forwarding table so multicast frames are sent only to interested receivers.
Related concept
Access ports place end devices into a single VLAN.
- ✓
IGMP snooping builds a Layer 2 forwarding table that maps multicast MAC addresses to switch ports.
Why this is correct
Correct because the snooping switch records which ports have active members for each multicast group, using the multicast MAC address derived from the IP group address.
Related concept
Access ports place end devices into a single VLAN.
- ✓
IGMP snooping forwards IGMP membership reports only toward the multicast router (querier).
Why this is correct
Correct because the switch forwards IGMP reports only out of the port where the querier (multicast router) is connected, preventing unnecessary flooding to other hosts.
Related concept
Access ports place end devices into a single VLAN.
- ✗
IGMP snooping suppresses all IGMP general queries from the multicast router.
Why it's wrong here
Incorrect because IGMP snooping does not suppress queries; it forwards them to all ports in the VLAN so hosts can respond. Queries are only suppressed in IGMP proxy reporting, which is a different feature.
- ✗
IGMP snooping requires PIM to be enabled on the switch.
Why it's wrong here
Incorrect because IGMP snooping operates at Layer 2 and does not require PIM; it is independent of Layer 3 multicast routing protocols.
Common exam traps
Common exam trap: an active trunk can still block the VLAN you need
A trunk being up does not prove every VLAN is crossing it. Check allowed VLAN lists, native VLAN mismatch, VLAN existence and access-port assignment.
Detailed technical explanation
How to think about this question
VLAN questions usually combine access-port and trunking clues. The key is to identify whether the issue is local to one switchport, caused by the trunk, or caused by the VLAN not existing where it needs to exist.
KKey Concepts to Remember
- Access ports place end devices into a single VLAN.
- Trunk ports carry multiple VLANs between switches.
- Allowed VLAN lists decide which VLANs can cross a trunk.
- Native VLAN mismatch can create confusing symptoms.
TExam Day Tips
- Use show vlan brief to verify access VLANs.
- Use show interfaces trunk to verify trunk state and allowed VLANs.
- Do not treat every same-VLAN issue as a routing problem.
Key takeaway
A trunk being up does not mean the VLAN is allowed across it. Always verify the allowed VLAN list and whether the VLAN exists on both switches.
Real-world example
How this comes up in practice
A help-desk technician troubleshoots why a newly connected PC cannot reach shared printers on the same floor. The cable is good, the switch port is active, but the PC is in VLAN 20 and the printers are in VLAN 10. The uplink trunk only allows VLAN 10. A trunk being up does not mean every VLAN crosses it.
What to study next
Got this wrong? Here's your next step.
Review VLAN allowed lists, native VLAN mismatch detection, and how to verify VLAN membership with show vlan brief and show interfaces trunk. Then practise related 350-401 questions on switching, trunking, and access-port configuration.
- →
IP Multicast — study guide chapter
Learn the concepts, then practise the questions
- →
IP Multicast practice questions
Targeted practice on this topic area only
- →
All 350-401 questions
2,015 questions across all exam domains
- →
ENCOR 350-401 study guide
Full concept coverage aligned to exam objectives
- →
350-401 practice test guide
How to use practice tests most effectively before exam day
Related practice questions
Related 350-401 practice-question pages
Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.
Architecture practice questions
Practise 350-401 questions linked to Architecture.
Enterprise Network Design practice questions
Practise 350-401 questions linked to Enterprise Network Design.
SD-Access Architecture practice questions
Practise 350-401 questions linked to SD-Access Architecture.
SD-WAN Architecture practice questions
Practise 350-401 questions linked to SD-WAN Architecture.
QoS Architecture practice questions
Practise 350-401 questions linked to QoS Architecture.
Virtualization practice questions
Practise 350-401 questions linked to Virtualization.
Network Function Virtualization practice questions
Practise 350-401 questions linked to Network Function Virtualization.
Virtual Machines and Hypervisors practice questions
Practise 350-401 questions linked to Virtual Machines and Hypervisors.
VRF and Path Isolation practice questions
Practise 350-401 questions linked to VRF and Path Isolation.
Infrastructure practice questions
Practise 350-401 questions linked to Infrastructure.
OSPF practice questions
Practise 350-401 questions linked to OSPF.
BGP practice questions
Practise 350-401 questions linked to BGP.
Practice this exam
Start a free 350-401 practice session
Short sessions build daily habit. Longer sessions build exam-day stamina. Try a timed session to simulate real conditions.
FAQ
Questions learners often ask
What does this 350-401 question test?
IP Multicast — This question tests IP Multicast — Access ports place end devices into a single VLAN..
What is the correct answer to this question?
The correct answer is: IGMP snooping reduces multicast flooding on a VLAN by forwarding traffic only to ports that have joined the group. — IGMP snooping optimizes multicast forwarding at Layer 2 by monitoring IGMP messages. It builds a snooping table, forwards reports only to the querier, and can be configured with static entries. It does not suppress queries or require PIM.
What should I do if I get this 350-401 question wrong?
Review VLAN allowed lists, native VLAN mismatch detection, and how to verify VLAN membership with show vlan brief and show interfaces trunk. Then practise related 350-401 questions on switching, trunking, and access-port configuration.
What is the key concept behind this question?
Access ports place end devices into a single VLAN.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Last reviewed: Jun 18, 2026
This 350-401 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 350-401 exam.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.