PCNE Implementing VPC Instances Practice Question
You need to configure firewall rules to allow HTTP (TCP 80) traffic from the internet to instances in a VPC. The instances are in different subnets and have a network tag 'web-server'. You want to minimize the number of rules. Which rule configuration is correct?
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
✓
Create an ingress rule with source 0.0.0.0/0, tcp:80, and target tags 'web-server'.
Firewall rules are global, so one ingress rule can apply to all instances with the tag 'web-server' regardless of subnet. The direction must be ingress, source 0.0.0.0/0, protocol tcp:80, and target tags 'web-server'.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Create an ingress rule with source 0.0.0.0/0, protocol tcp:0-65535, and target tags 'web-server'.
Why it's wrong here
This would allow all TCP ports, which is overly permissive.
- ✗
Create an egress rule with source 0.0.0.0/0, tcp:80, and target tags 'web-server'.
Why it's wrong here
Egress rules control outbound traffic; for incoming traffic, ingress rule is needed.
- ✓
Create an ingress rule with source 0.0.0.0/0, tcp:80, and target tags 'web-server'.
Why this is correct
This single ingress rule allows HTTP from any source to instances tagged 'web-server'.
- ✗
Create an ingress rule for each subnet with source 0.0.0.0/0, tcp:80, and target tags 'web-server'.
Why it's wrong here
Unnecessary duplication; a single global rule with target tags applies to all matching instances.
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Written by Johnson Ajibi, MSc IT Security
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