TF-003 Interact with Terraform modules Practice Question
This TF-003 practice question tests your understanding of interact with terraform modules. 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.
Exhibit
Refer to the exhibit.
```hcl
module "networking" {
source = "./modules/networking"
vpc_cidr = "10.0.0.0/16"
}
```
The module in `./modules/networking` has `variables.tf`:
```hcl
variable "vpc_cidr" {
description = "CIDR block for the VPC"
type = string
}
variable "environment" {
description = "Environment name"
type = string
}
```
After running `terraform plan`, the user receives an error: `Error: Missing required variable`. The variable 'vpc_cidr' is provided. 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 module requires a variable 'environment' that is not passed.
The module defines a second required variable 'environment' that has no default value and is not set in the module block, causing the error. Option B is wrong because 'vpc_cidr' is provided. Option C is wrong because syntax is correct. Option D is wrong because there is no conflict; the variable is simply unset.
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 module requires a variable 'environment' that is not passed.
Why this is correct
The module's variables.tf declares 'environment' without a default, so it must be set.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
The syntax is correct for a module block; the issue is missing arguments.
✗
The variable 'vpc_cidr' is misspelled.
Why it's wrong here
The variable name matches; the error is about a missing variable, not misspelling.
✗
The variable 'vpc_cidr' conflicts with a provider variable.
Why it's wrong here
There is no conflict; the error clearly indicates a missing variable.
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 network engineer segments a warehouse floor into three subnets: 20 scanners, 5 printers, and 2 management hosts. Picking the wrong mask wastes addresses or leaves too few usable hosts. Exam questions test whether you can apply CIDR notation, calculate block size, and identify the correct usable-host range for a given prefix.
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 TF-003 subnetting questions on CIDR, address ranges, and subnet selection.
Interact with Terraform modules — This question tests Interact with Terraform modules — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: The module requires a variable 'environment' that is not passed. — The module defines a second required variable 'environment' that has no default value and is not set in the module block, causing the error. Option B is wrong because 'vpc_cidr' is provided. Option C is wrong because syntax is correct. Option D is wrong because there is no conflict; the variable is simply unset.
What should I do if I get this TF-003 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 TF-003 subnetting questions on CIDR, address ranges, and subnet selection.
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?
CIDR notation defines the prefix length.
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