The answer is the global command 'ip multicast-routing' must be enabled. This command is the fundamental prerequisite for any multicast forwarding on a Cisco router; without it, the router will not build a multicast routing table or create (S,G) entries, regardless of PIM configuration on individual interfaces. In the ENCOR 350-401 exam, this is a classic trick—candidates often enable PIM sparse mode and configure a static RP but forget the global toggle, leading to a silent failure where the router receives traffic but never installs a route. The exam tests your understanding that multicast routing is disabled by default and requires an explicit global activation. A common memory tip is to think of it as the "master switch": just as you need to enable IP routing globally before dynamic routing protocols work, you must enable 'ip multicast-routing' before any multicast protocol can function. Remember: PIM on interfaces is useless without the global command.
CCNP 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.
An engineer is configuring multicast on a Cisco router. The router receives multicast traffic from a source on interface GigabitEthernet0/0 and needs to forward it to receivers on interface GigabitEthernet0/1. The engineer enables PIM sparse mode on both interfaces and configures a static RP. However, the router does not create a multicast routing entry for the (S,G) pair. What is the most likely missing configuration?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
The global command 'ip multicast-routing' is not configured.
Correct because this command is required to enable multicast routing on the router.
B
The interface GigabitEthernet0/0 is not configured with an IP address.
Why wrong: Incorrect because the interface must have an IP address, but the scenario implies it is receiving traffic, so it likely has an IP.
C
The RP address is not reachable from the router.
Why wrong: Incorrect because the RP is needed for group-to-RP mapping, but the (S,G) entry should still be created if the source is directly connected.
D
The router is not configured as a candidate RP.
Why wrong: Incorrect because the router does not need to be an RP to forward multicast traffic.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The global command 'ip multicast-routing' is not configured.
For multicast routing to work, the 'ip multicast-routing' command must be enabled globally. Without it, the router will not create multicast forwarding entries, even if PIM is enabled on interfaces.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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 global command 'ip multicast-routing' is not configured.
Why this is correct
Correct because this command is required to enable multicast routing on the router.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The interface GigabitEthernet0/0 is not configured with an IP address.
Why it's wrong here
Incorrect because the interface must have an IP address, but the scenario implies it is receiving traffic, so it likely has an IP.
✗
The RP address is not reachable from the router.
Why it's wrong here
Incorrect because the RP is needed for group-to-RP mapping, but the (S,G) entry should still be created if the source is directly connected.
✗
The router is not configured as a candidate RP.
Why it's wrong here
Incorrect because the router does not need to be an RP to forward multicast traffic.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Trap categories for this question
Scenario analysis trap
Incorrect because the interface must have an IP address, but the scenario implies it is receiving traffic, so it likely has an IP.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
Use explanations to understand the rule behind the answer.
TExam Day Tips
→Underline the problem statement mentally.
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A practitioner preparing for the 350-401 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Got this wrong? Here's your next step.
Identify which 350-401 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
IP Multicast — This question tests IP Multicast — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The global command 'ip multicast-routing' is not configured. — For multicast routing to work, the 'ip multicast-routing' command must be enabled globally. Without it, the router will not create multicast forwarding entries, even if PIM is enabled on interfaces.
What should I do if I get this 350-401 question wrong?
Identify which 350-401 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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