The answer is PIM Sparse-Mode. PIM Sparse-Mode requires a rendezvous point (RP) to function because it uses a pull model where receivers must explicitly join the RP to receive traffic, and sources register with the RP to announce their existence. Without an RP, there is no central meeting point for sources and receivers, so multicast traffic cannot be distributed in sparse-mode. On the ENCOR 350-401 exam, this question tests your understanding of multicast protocols and their architectural requirements; a common trap is confusing PIM Sparse-Mode with PIM Dense-Mode, which uses flood-and-prune and never needs an RP. Another trap is assuming Bidirectional PIM does not require an RP—it does, but with a different, shared-tree-only mechanism. For a quick memory tip: think “Sparse = Single RP” or remember the mnemonic “SM needs RP, DM floods free.”
350-401 IP Multicast Practice Question
This 350-401 practice question tests your understanding of ip multicast. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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 PIM mode requires a rendezvous point (RP) to function?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
PIM Sparse-Mode
PIM sparse-mode (SM) requires an RP to act as a meeting point for receivers and sources. Dense-mode uses flood-and-prune without an RP, and bidirectional PIM also uses an RP but with a different mechanism.
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.
✗
PIM Dense-Mode
Why it's wrong here
Incorrect. Dense-mode does not use an RP; it floods traffic and prunes branches.
✓
PIM Sparse-Mode
Why this is correct
Correct. Sparse-mode requires an RP to manage group membership.
Related concept
Read the scenario before looking for a memorised answer.
✗
PIM Sparse-Dense-Mode
Why it's wrong here
Incorrect. Sparse-dense-mode can operate without an RP for groups that fall back to dense-mode.
✗
PIM Bidirectional
Why it's wrong here
Incorrect. Bidirectional PIM also uses an RP, but the question asks for the mode that requires one; sparse-mode is the most common answer.
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.
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 350-401 question in full detail.
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: PIM Sparse-Mode — PIM sparse-mode (SM) requires an RP to act as a meeting point for receivers and sources. Dense-mode uses flood-and-prune without an RP, and bidirectional PIM also uses an RP but with a different mechanism.
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.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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