AWS - VPC Fundamentals
After attaching an Internet Gateway and updating the route table, your EC2 instances in the public subnet still cannot access the internet. What is the most probable cause?
After attaching an Internet Gateway and updating the route table, your EC2 instances in the public subnet still cannot access the internet. What is the most probable cause?
medium📝 Debug Q7 of 15
Step-by-Step Solution
Solution:
Step 1: Verify Internet Gateway attachment and route table
Since the Internet Gateway is attached and the route table has the correct route, these are not the issues.Step 2: Check instance IP addressing
Instances in a public subnet require public IP addresses to communicate with the internet directly through the Internet Gateway.Step 3: Evaluate security groups and NACLs
Security groups allowing outbound traffic and NACLs allowing inbound HTTP traffic are necessary but not sufficient if instances lack public IPs.Final Answer:
Instances do not have public IP addresses assigned -> Option CQuick Check:
Public IP required for internet access via Internet Gateway [OK]
Quick Trick: Public IP needed for internet access in public subnet [OK]
Common Mistakes:
- Assuming security groups alone enable internet access
- Ignoring the need for public IP addresses
- Confusing DHCP options with internet connectivity
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