The answer is to set the hostkey_verify parameter to False in the ncclient connect method. This is correct because ncclient’s connect function performs SSH host key checking by default, comparing the switch’s public key against the local known_hosts file. When a host key has changed or is missing—common after a device replacement or OS upgrade—the authentication fails even with valid credentials. Disabling hostkey_verify bypasses this check, allowing the NETCONF session to proceed. On the Cisco DevNet Associate 200-901 exam, this scenario tests your understanding of NETCONF transport security and the ncclient library’s configuration options. A common trap is to assume the error is always credential-based, but the exam wants you to recognize that SSH host key mismatches produce authentication errors too. Remember the memory tip: “Host key mismatch? Set hostkey_verify to False to bypass the check.”
200-901 Software Development and Design Practice Question
This 200-901 practice question tests your understanding of software development and design. 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 is developing a Python script to automate the collection of interface statistics from multiple Cisco Catalyst switches using NETCONF. The engineer uses the 'ncclient' library to connect to each switch. The script works for most switches, but for one switch, the connection consistently fails with an authentication error. The engineer has verified that the username and password are correct and that the switch has NETCONF enabled. The engineer suspects the issue might be related to SSH host key checking. The engineer wants to modify the script to bypass host key checking for this specific switch. Which approach should the engineer use?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Set the 'hostkey_verify' parameter to False in the connect method
Option A is correct because the 'ncclient' library's connect method accepts a 'hostkey_verify' parameter. Setting it to False disables SSH host key checking, which bypasses the verification of the switch's host key against the known_hosts file. This resolves authentication errors caused by host key mismatches, such as when the switch's host key has changed or is not present in the known_hosts file.
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.
✓
Set the 'hostkey_verify' parameter to False in the connect method
Why this is correct
Correct: This disables host key verification.
Related concept
Read the scenario before looking for a memorised answer.
✗
Disable SSH key-based authentication by setting 'look_for_keys=False'
Why it's wrong here
Incorrect: This disables key auth, not host key checking.
✗
Use the 'allow_agent' parameter set to False
Why it's wrong here
Incorrect: This disables the SSH agent, not host key checking.
✗
Set the 'known_hosts' parameter to an empty file in the connect method
Why it's wrong here
Incorrect: ncclient does not have a 'known_hosts' parameter.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between SSH host key verification and SSH key-based authentication, leading candidates to confuse parameters like 'look_for_keys' (which controls key-based login) with 'hostkey_verify' (which controls host key trust).
Detailed technical explanation
How to think about this question
Under the hood, ncclient uses Paramiko for SSH transport. Paramiko's default behavior is to verify the remote host's SSH host key against the user's known_hosts file (typically ~/.ssh/known_hosts). When 'hostkey_verify=False' is set, ncclient passes this to Paramiko's 'MissingHostKeyPolicy' set to 'AutoAddPolicy' or 'WarningPolicy', effectively skipping the verification. In real-world automation, this is often used in lab environments or when switches are frequently rebuilt, causing host key changes, but it should be avoided in production due to security risks like man-in-the-middle attacks.
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 200-901 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.
Software Development and Design — This question tests Software Development and Design — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Set the 'hostkey_verify' parameter to False in the connect method — Option A is correct because the 'ncclient' library's connect method accepts a 'hostkey_verify' parameter. Setting it to False disables SSH host key checking, which bypasses the verification of the switch's host key against the known_hosts file. This resolves authentication errors caused by host key mismatches, such as when the switch's host key has changed or is not present in the known_hosts file.
What should I do if I get this 200-901 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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