Quick Answer
The answer is that the NETCONF feature has not been enabled on the NX-OS switch. A "Connection refused" error is distinct from a timeout or unreachable host—it means the switch actively rejected the TCP handshake on port 830, which is the default NETCONF-over-SSH port. This rejection occurs because the NETCONF subsystem is not running; on NX-OS, the `netconf` feature must be explicitly enabled with the `feature netconf` command to start the server process that listens on that port. On the Cisco DCCOR 350-601 exam, this scenario tests your understanding of NETCONF’s dependency on feature activation, often appearing as a distractor where candidates mistakenly troubleshoot SSH or ACL issues instead. A common trap is assuming NETCONF is automatically available once SSH is configured, but it requires a separate feature enablement. Memory tip: think "No feature, no port 830"—if you see "Connection refused" on NX-OS, always verify `show feature | include netconf` first.
This 350-601 practice question tests your understanding of automation. 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 NETCONF session to an NX-OS switch fails with 'Connection refused'. 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.
All of the above
Why wrong: Only A is the direct cause; B and C are less specific.
Wrong SSH port (default 830)
Why wrong: This is configurable, but 'Connection refused' means the port is not open.
The switch is unreachable
Why wrong: Unreachable would result in 'No route to host' or timeout.
NETCONF is not enabled on the switch
Without 'feature netconf', the NETCONF server does not start.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
NETCONF is not enabled on the switch
NETCONF uses SSH port 830 by default, but the 'Connection refused' error specifically indicates that the TCP connection was actively rejected by the switch, not that it timed out or was unreachable. This occurs when the NETCONF subsystem is not available because the 'netconf' feature has not been enabled on the NX-OS device, which is required to start the NETCONF server process.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
All of the above
Why it's wrong here
Only A is the direct cause; B and C are less specific.
Wrong SSH port (default 830)
Why it's wrong here
This is configurable, but 'Connection refused' means the port is not open.
The switch is unreachable
Why it's wrong here
Unreachable would result in 'No route to host' or timeout.
NETCONF is not enabled on the switch
Why this is correct
Without 'feature netconf', the NETCONF server does not start.
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.
Common exam traps
Cisco often tests the distinction between 'Connection refused' (service not running) and 'Connection timed out' (host unreachable or firewall blocking), leading candidates to incorrectly select 'wrong port' or 'unreachable' when the real issue is that the NETCONF feature is not enabled.
Detailed technical explanation
On NX-OS, NETCONF is implemented as a feature that must be explicitly enabled with the 'feature netconf' command, which starts the NETCONF server listening on TCP port 830. The 'Connection refused' error is a TCP RST response sent by the switch's TCP stack when no application is bound to the requested port, which is exactly what happens when the NETCONF feature is disabled. In contrast, an incorrect port would not trigger a RST unless that port is actively closed by the switch's firewall or ACL.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A practitioner preparing for the 350-601 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
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
Automation — This question tests Automation — Read the scenario before looking for a memorised answer..
The correct answer is: NETCONF is not enabled on the switch — NETCONF uses SSH port 830 by default, but the 'Connection refused' error specifically indicates that the TCP connection was actively rejected by the switch, not that it timed out or was unreachable. This occurs when the NETCONF subsystem is not available because the 'netconf' feature has not been enabled on the NX-OS device, which is required to start the NETCONF server process.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 24, 2026
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