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 developer is designing a Python script to parse the output of 'show ip interface brief' from a Cisco IOS device. The output is stored in a string variable. The developer wants to extract only the interfaces that are up/up. The current code uses regular expressions but often fails because the interface names contain special characters (e.g., GigabitEthernet1/0/1). Which approach should the developer use to reliably parse the output?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use a structured data format like JSON or YAML if available from the device
The most reliable approach is to use structured output if the device supports JSON or YAML output (e.g., 'show ip interface brief | json' on IOS-XE). This avoids regex pitfalls. Option A (split on whitespace) may break if interface names contain spaces (they don't, but slashes are fine). Option B (CSV parser) is not appropriate for this output. Option D (complex regex) is possible but less maintainable and error-prone.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Use the 're' module with a more complex pattern that escapes special characters
Why it's wrong here
While possible, regex is brittle and hard to maintain; structured output is preferred.
✗
Use split on whitespace and check column values
Why it's wrong here
This may work for simple lines but fails if interface names contain spaces or if column alignment changes.
✓
Use a structured data format like JSON or YAML if available from the device
Why this is correct
Structured output is consistent, machine-readable, and immune to formatting changes.
Related concept
Static NAT maps one inside address to one outside address.
✗
Use a CSV parser with a custom delimiter
Why it's wrong here
The output is not CSV; there is no consistent delimiter.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Trap categories for this question
Command / output trap
While possible, regex is brittle and hard to maintain; structured output is preferred.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
→Identify inside and outside interfaces first.
→Check whether the scenario needs static NAT, dynamic NAT or PAT.
→Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Real-world example
How this comes up in practice
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
Got this wrong? Here's your next step.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related 200-901 NAT questions on configuration and troubleshooting.
Software Development and Design — This question tests Software Development and Design — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: Use a structured data format like JSON or YAML if available from the device — The most reliable approach is to use structured output if the device supports JSON or YAML output (e.g., 'show ip interface brief | json' on IOS-XE). This avoids regex pitfalls. Option A (split on whitespace) may break if interface names contain spaces (they don't, but slashes are fine). Option B (CSV parser) is not appropriate for this output. Option D (complex regex) is possible but less maintainable and error-prone.
What should I do if I get this 200-901 question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related 200-901 NAT questions on configuration and troubleshooting.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
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