The correct answer is that the router uses 172.16.1.1 as the RP for all multicast groups, with PIM sparse-mode enabled on both interfaces. This is because the `ip pim rp-address 172.16.1.1` command statically assigns that IP as the rendezvous point for every multicast group, overriding any dynamic RP discovery mechanisms. The `ip pim sparse-mode` under each interface forces those links to operate in sparse mode, meaning they will only forward multicast traffic when explicitly joined via the RP. On the ENCOR 350-401 exam, this tests your understanding of PIM sparse-mode static RP configuration and verification, often appearing as a scenario where you must distinguish between static and dynamic RP assignment. A common trap is assuming the RP must be a loopback or that the command only applies to specific groups—here, no ACL is used, so it applies to all groups. Memory tip: “Static RP, no ACL—all groups, one address.”
350-401 Enterprise Network Design Practice Question
This 350-401 practice question tests your understanding of enterprise network design. 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.
Given this configuration:
interface GigabitEthernet0/0
ip address 172.16.1.1 255.255.255.0
ip pim sparse-mode
!
interface GigabitEthernet0/1
ip address 172.16.2.1 255.255.255.0
ip pim sparse-mode
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The router uses 172.16.1.1 as the RP for all multicast groups, and PIM sparse-mode is enabled on both interfaces.
The configuration statically assigns 172.16.1.1 as the RP for all multicast groups using the 'ip pim rp-address' command, and both interfaces are explicitly configured with 'ip pim sparse-mode'. This ensures that PIM sparse-mode is operational on the interfaces and that the router uses the specified RP for group-to-RP mapping, making option A correct.
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 router uses 172.16.1.1 as the RP for all multicast groups, and PIM sparse-mode is enabled on both interfaces.
Why this is correct
The 'ip pim rp-address' command statically assigns the RP, and sparse-mode is enabled on the interfaces.
Related concept
Read the scenario before looking for a memorised answer.
✗
The router will automatically elect an RP using BSR because no RP is configured.
Why it's wrong here
An RP is explicitly configured; BSR is not used unless configured.
✗
PIM dense-mode is used because sparse-mode is not fully configured.
Why it's wrong here
Sparse-mode is explicitly configured; dense-mode is not used.
✗
The configuration is invalid because the RP address must be a loopback interface.
Why it's wrong here
The RP address can be any interface IP; loopback is recommended but not required.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that the RP must be a loopback interface for stability, but the command accepts any reachable IP address, including a physical interface, as long as it is configured with 'ip pim sparse-mode' or 'ip pim sparse-dense-mode'.
Detailed technical explanation
How to think about this question
In PIM sparse-mode, the RP is the root of the shared tree (RPT) for all multicast sources. The 'ip pim rp-address' command statically maps all multicast groups to the specified RP, overriding any dynamic RP discovery mechanisms like BSR or Auto-RP. This configuration is common in small networks where manual RP assignment is preferred for simplicity and control, but it lacks redundancy if the RP interface fails.
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.
TExam Day Tips
→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.
Enterprise Network Design — This question tests Enterprise Network Design — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The router uses 172.16.1.1 as the RP for all multicast groups, and PIM sparse-mode is enabled on both interfaces. — The configuration statically assigns 172.16.1.1 as the RP for all multicast groups using the 'ip pim rp-address' command, and both interfaces are explicitly configured with 'ip pim sparse-mode'. This ensures that PIM sparse-mode is operational on the interfaces and that the router uses the specified RP for group-to-RP mapping, making option A correct.
What should I do if I get this 350-401 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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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