AWS - Security Groups and Network ACLs
A Security Group attached to an EC2 instance allows inbound traffic on port 8080, but the instance cannot receive traffic on that port. What is the most likely cause?
A Security Group attached to an EC2 instance allows inbound traffic on port 8080, but the instance cannot receive traffic on that port. What is the most likely cause?
medium📝 Debug Q7 of 15
Step-by-Step Solution
Solution:
Step 1: Check Network ACL rules
If NACL denies inbound on port 8080, traffic is blocked before reaching instance.Step 2: Confirm Security Group allows inbound
Security Group allows inbound, so it is not the cause.Final Answer:
Network ACL denies inbound traffic on port 8080 -> Option BQuick Check:
Subnet-level NACL deny blocks traffic despite Security Group allow [OK]
Quick Trick: NACL deny beats Security Group allow for inbound traffic [OK]
Common Mistakes:
MISTAKES- Blaming Security Group outbound rules
- Ignoring subnet-level NACL rules
- Assuming route table or instance firewall is always the cause
Master "Security Groups and Network ACLs" in AWS
Want More Practice?
15+ quiz questions · All difficulty levels · Free
Free Signup - Practice All QuestionsMore AWS Quizzes