Question 1,088 of 2,152

SNMP Troubleshooting →easyMultiple ChoiceObjective-mapped

SNMPv2c Write Failure: Same Community String for RO and RW

This 300-410 practice question tests your understanding of snmp troubleshooting. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 configures SNMPv2c on router R3 with 'snmp-server community cisco RO' and 'snmp-server community cisco RW'. The NMS can poll read-only data but fails when trying to write a configuration value. The NMS uses the RW community string. What is the most likely cause?

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.

A
The community string 'cisco' is used for both RO and RW; the router applies the first matching community, which is RO.
Correct because identical community strings cause the router to use the RO access, preventing writes.
B
The NMS is sending the community string in uppercase, but the router expects lowercase.
Why wrong: Incorrect because community strings are case-sensitive, but the NMS would fail for both RO and RW if case mismatched.
C
The router needs the 'snmp-server enable traps' command to allow write operations.
Why wrong: Incorrect because enabling traps is unrelated to write access.
D
The NMS must use SNMPv3 for write operations; SNMPv2c does not support writes.
Why wrong: Incorrect because SNMPv2c supports write operations with the RW community.

Full breakdown with real-world context →

Quick Answer

The answer is that using the same community string for both RO and RW causes the router to apply the read-only privilege first, blocking write operations. This occurs because Cisco IOS processes community strings in the order they are configured; when 'snmp-server community cisco RO' is entered before 'snmp-server community cisco RW', the router binds the string 'cisco' exclusively to read-only access, ignoring the subsequent RW assignment. On the Cisco CCNP ENARSI 300-410 exam, this scenario tests your understanding of SNMPv2c community string precedence and the common misconfiguration where an engineer assumes identical strings grant both privileges. The trap is that the NMS can poll successfully, leading you to suspect ACLs or version mismatches, but the root cause is the duplicate string. A simple memory tip: "First match locks the privilege—RO before RW means no write."

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

✓

The community string 'cisco' is used for both RO and RW; the router applies the first matching community, which is RO.

When two SNMPv2c community strings are identical (both 'cisco'), the router applies the first matching entry in its configuration. Since 'snmp-server community cisco RO' is configured before 'snmp-server community cisco RW', the router treats all requests using 'cisco' as read-only, regardless of the intended access level. This prevents write operations even when the NMS correctly sends the RW community string.

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 community string 'cisco' is used for both RO and RW; the router applies the first matching community, which is RO.
Why this is correct
Correct because identical community strings cause the router to use the RO access, preventing writes.
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 NMS is sending the community string in uppercase, but the router expects lowercase.
Why it's wrong here
Incorrect because community strings are case-sensitive, but the NMS would fail for both RO and RW if case mismatched.
✗
The router needs the 'snmp-server enable traps' command to allow write operations.
Why it's wrong here
Incorrect because enabling traps is unrelated to write access.
✗
The NMS must use SNMPv3 for write operations; SNMPv2c does not support writes.
Why it's wrong here
Incorrect because SNMPv2c supports write operations with the RW community.

Common exam traps

Common exam trap: answer the scenario, not the keyword

Cisco often tests the subtlety that identical community strings with different access levels cause the first-configured entry to take precedence, leading candidates to overlook the order of configuration lines.

Detailed technical explanation

How to think about this question

Cisco IOS processes SNMP community strings in the order they appear in the running configuration. When duplicate community strings exist, only the first match is applied, and subsequent identical strings are ignored. This behavior is documented in Cisco's SNMP configuration guide and can be verified by examining the output of 'show snmp community', which will list only the RO entry if both strings are identical. In real-world scenarios, this often occurs during automated provisioning or when configuration snippets are appended without checking for duplicates.

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 300-410 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 exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.

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FAQ

Questions learners often ask

What does this 300-410 question test?

SNMP Troubleshooting — This question tests SNMP Troubleshooting — Read the scenario before looking for a memorised answer..

What is the correct answer to this question?

The correct answer is: The community string 'cisco' is used for both RO and RW; the router applies the first matching community, which is RO. — When two SNMPv2c community strings are identical (both 'cisco'), the router applies the first matching entry in its configuration. Since 'snmp-server community cisco RO' is configured before 'snmp-server community cisco RW', the router treats all requests using 'cisco' as read-only, regardless of the intended access level. This prevents write operations even when the NMS correctly sends the RW community string.

What should I do if I get this 300-410 question wrong?

Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.

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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