Question 1,133 of 1,733
Operations and MaintenancehardMultiple ChoiceObjective-mapped

PAS-C01 Operations and Maintenance Practice Question

This PAS-C01 practice question tests your understanding of operations and maintenance. 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.

Exhibit

Refer to the exhibit.

```
{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Action": [
        "ec2:DescribeInstances",
        "ec2:StartInstances",
        "ec2:StopInstances"
      ],
      "Resource": "*"
    },
    {
      "Effect": "Allow",
      "Action": "s3:GetObject",
      "Resource": "arn:aws:s3:::sap-backups/*"
    }
  ]
}
```

An SAP administrator is troubleshooting an issue where an AWS Lambda function is unable to start an EC2 instance. The Lambda execution role has the IAM policy shown in the exhibit. What is the likely cause of the failure?

Exhibit

Refer to the exhibit.

```
{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Action": [
        "ec2:DescribeInstances",
        "ec2:StartInstances",
        "ec2:StopInstances"
      ],
      "Resource": "*"
    },
    {
      "Effect": "Allow",
      "Action": "s3:GetObject",
      "Resource": "arn:aws:s3:::sap-backups/*"
    }
  ]
}
```

Answer choices

Why each option matters

Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.

Correct answer & explanation

The Lambda function is not configured with the correct VPC subnet or security group to reach the EC2 instance.

The issue is likely that the Lambda function is not configured with the correct VPC subnet or security group to reach the EC2 instance. Lambda functions running in a VPC require proper networking configuration to interact with EC2 instances in the same VPC. The IAM policy shown allows ec2:StartInstances, ec2:DescribeInstances, and s3:GetObject on the specified resources, so IAM permissions are not the problem. Option A is correct because networking misconfiguration is a common cause of such failures. Options B, C, and D are incorrect as the policy does grant the necessary permissions.

Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.

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 Lambda function is not configured with the correct VPC subnet or security group to reach the EC2 instance.

    Why this is correct

    Lambda may need VPC access to start instances in a VPC, but the policy is fine.

    Related concept

    CIDR notation defines the prefix length.

  • The policy does not allow ec2:DescribeInstances.

    Why it's wrong here

    The policy allows ec2:DescribeInstances.

  • The policy does not allow ec2:StartInstances.

    Why it's wrong here

    The policy explicitly allows ec2:StartInstances on all resources.

  • The policy does not allow s3:GetObject on the specific backup object.

    Why it's wrong here

    The policy allows s3:GetObject on any object in the sap-backups bucket.

Common exam traps

Common exam trap: usable hosts are not the same as total addresses

Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.

Detailed technical explanation

How to think about this question

Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.

KKey Concepts to Remember

  • CIDR notation defines the prefix length.
  • Block size helps identify subnet boundaries.
  • Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
  • The required host count determines the smallest suitable subnet.

TExam Day Tips

  • Write the block size before choosing the subnet.
  • Check whether the question asks for hosts, subnets or a specific address range.
  • Do not confuse /24, /25, /26 and /27 host counts.

Key takeaway

Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.

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.

Visual reference

192.168.1.0 /24 256 addresses (254 usable) 192.168.1.0 /25 Subnet A 128 addr (126 usable) 192.168.1.128 /25 Subnet B 128 addr (126 usable) Borrowing 1 bit from host portion creates 2 subnets (/25)

Quick reference

AWS S3 Storage Class Comparison

Storage ClassMin DurationRetrievalUse Case
S3 StandardNoneImmediateFrequently accessed data
S3 Standard-IA30 daysImmediateInfrequent access, rapid retrieval
S3 One Zone-IA30 daysImmediateNon-critical infrequent data
S3 Intelligent-TieringNoneImmediate–hoursUnknown or changing access patterns
S3 Glacier Instant90 daysMillisecondsArchive with instant retrieval
S3 Glacier Flexible90 daysMinutes–hoursArchive, flexible retrieval
S3 Glacier Deep Archive180 daysHoursLong-term compliance archive

What to study next

Got this wrong? Here's your next step.

Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related PAS-C01 subnetting questions on CIDR, address ranges, and subnet selection.

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FAQ

Questions learners often ask

What does this PAS-C01 question test?

Operations and Maintenance — This question tests Operations and Maintenance — CIDR notation defines the prefix length..

What is the correct answer to this question?

The correct answer is: The Lambda function is not configured with the correct VPC subnet or security group to reach the EC2 instance. — The issue is likely that the Lambda function is not configured with the correct VPC subnet or security group to reach the EC2 instance. Lambda functions running in a VPC require proper networking configuration to interact with EC2 instances in the same VPC. The IAM policy shown allows ec2:StartInstances, ec2:DescribeInstances, and s3:GetObject on the specified resources, so IAM permissions are not the problem. Option A is correct because networking misconfiguration is a common cause of such failures. Options B, C, and D are incorrect as the policy does grant the necessary permissions.

What should I do if I get this PAS-C01 question wrong?

Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related PAS-C01 subnetting questions on CIDR, address ranges, and subnet selection.

What is the key concept behind this question?

CIDR notation defines the prefix length.

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Last reviewed: Jun 20, 2026

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