The answer is the condition restricts access to a specific IP range that does not include the AWS Glue service IPs. This is because the IAM policy uses an IP address condition key (aws:SourceIp) set to 10.0.0.0/24, which evaluates the source IP of the request as seen by the S3 service. However, AWS Glue jobs run inside a VPC and their requests to S3 originate from the Glue service principal’s IP addresses, not from the private IPs of the job’s VPC resources, and those service IPs fall outside the allowed range, causing the Access Denied error. On the AWS Certified Machine Learning Specialty MLS-C01 exam, this tests your understanding of how IAM policy IP conditions interact with managed AWS services like Glue—a common trap is assuming that a job’s VPC subnet IPs are used as the source. The fix is to remove the IP condition or use a VPC endpoint with a condition key like aws:SourceVpce instead. Memory tip: Glue uses service IPs, not job IPs—so “Glue’s IPs are not your VPC’s IPs.”
MLS-C01 Data Engineering Practice Question
This MLS-C01 practice question tests your understanding of data engineering. 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 data engineer has attached the above IAM policy to an IAM role used by an AWS Glue ETL job. The job reads from and writes to 'my-data-bucket'. The job is failing with an Access Denied error. 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.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The condition restricts access to a specific IP range that does not include the AWS Glue service IPs.
The policy restricts access to requests originating from the IP range 10.0.0.0/24. AWS Glue jobs run in a VPC that uses private IPs, but the source IP condition is evaluated based on the IP address of the Glue service principal, which is not within that range. The condition should be removed or modified to allow access from the Glue service.
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.
✓
The condition restricts access to a specific IP range that does not include the AWS Glue service IPs.
Why this is correct
The condition requires the request source IP to be in 10.0.0.0/24, but Glue's IPs are different.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Static NAT maps one inside address to one outside address.
✗
The IAM role needs to have s3:ListBucket permission.
Why it's wrong here
While ListBucket may be needed, the immediate error is likely due to the IP condition.
✗
The IAM role does not have permission to list the bucket.
Why it's wrong here
The policy allows GetObject and PutObject, but not ListBucket, which might be needed for listing objects.
✗
The resource ARN should include the bucket itself, not just the objects.
Why it's wrong here
The bucket ARN is missing for bucket-level operations, but the error is Access Denied, not a policy syntax issue.
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.
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 media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
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 MLS-C01 NAT questions on configuration and troubleshooting.
Data Engineering — This question tests Data Engineering — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: The condition restricts access to a specific IP range that does not include the AWS Glue service IPs. — The policy restricts access to requests originating from the IP range 10.0.0.0/24. AWS Glue jobs run in a VPC that uses private IPs, but the source IP condition is evaluated based on the IP address of the Glue service principal, which is not within that range. The condition should be removed or modified to allow access from the Glue service.
What should I do if I get this MLS-C01 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 MLS-C01 NAT questions on configuration and troubleshooting.
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?
Static NAT maps one inside address to one outside address.
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