The correct answer is to use `| where cidrmatch("10.0.0.0/8", src_ip) | stats dc(dest_ip)`. This is the most efficient approach because `cidrmatch()` performs a bitwise comparison directly on the IP address, filtering out non-matching events early in the pipeline before the distinct count operation, which drastically reduces the dataset that `stats dc()` must process. On the SPLK-1003 exam, this question tests your understanding of efficient IP filtering with cidrmatch, a key concept for optimizing searches that involve network traffic analysis. A common trap is to use `regex` or `like` with string patterns on the IP field, which is slower and less accurate than the native CIDR function. Remember the memory tip: "CIDR first, stats last" — always apply your IP filter as early as possible to minimize the workload on aggregation commands.
SPLK-1003 Advanced Searching and Statistics Practice Question
This SPLK-1003 practice question tests your understanding of advanced searching and statistics. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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 search is producing results that include both internal and external traffic. The analyst wants to approximate the number of distinct destination IPs for internal traffic only, where internal IPs fall within the 10.0.0.0/8 range. Which approach is most efficient?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use | where cidrmatch("10.0.0.0/8", src_ip) | stats dc(dest_ip)
Option D is correct because it uses `where cidrmatch("10.0.0.0/8", src_ip)` to efficiently filter events to only those with source IPs in the 10.0.0.0/8 range before passing them to `stats dc(dest_ip)`. This approach leverages Splunk's built-in CIDR matching function, which performs a bitwise comparison on the IP address, and applies the filter early in the pipeline, reducing the dataset for the distinct count operation. It is the most efficient as it avoids unnecessary evaluations or string operations on non-matching events.
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.
✗
Use | search src_ip=10.* | stats dc(dest_ip)
Why it's wrong here
Wildcard may miss some addresses and is slower
✗
Use | rex field=src_ip to extract first octet and then filter
Why it's wrong here
Complex and less efficient
✗
Use | eval internal=if(cidrmatch("10.0.0.0/8", src_ip),1,0) | stats dc(dest_ip) by internal
Why it's wrong here
Works but adds extra computation
✓
Use | where cidrmatch("10.0.0.0/8", src_ip) | stats dc(dest_ip)
Why this is correct
Efficient subnet matching with cidrmatch
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often choose Option C because they think `eval` with `by` is equivalent to filtering, but they overlook that it processes all events and computes an unnecessary group for external traffic, making it less efficient than a simple `where` filter.
Detailed technical explanation
How to think about this question
The `cidrmatch` function in Splunk performs a bitwise AND between the IP address and the subnet mask, then compares it to the network address, which is O(1) per event and handles all private ranges defined in RFC 1918. Using `where` before `stats` ensures that only matching events are passed to the aggregation command, reducing memory and CPU usage compared to `eval` with `by` which processes all events. In large datasets, this filtering order can significantly impact search performance, especially when dealing with millions of events.
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 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.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Advanced Searching and Statistics — This question tests Advanced Searching and Statistics — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Use | where cidrmatch("10.0.0.0/8", src_ip) | stats dc(dest_ip) — Option D is correct because it uses `where cidrmatch("10.0.0.0/8", src_ip)` to efficiently filter events to only those with source IPs in the 10.0.0.0/8 range before passing them to `stats dc(dest_ip)`. This approach leverages Splunk's built-in CIDR matching function, which performs a bitwise comparison on the IP address, and applies the filter early in the pipeline, reducing the dataset for the distinct count operation. It is the most efficient as it avoids unnecessary evaluations or string operations on non-matching events.
What should I do if I get this SPLK-1003 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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