AWS - Security Groups and Network ACLs
If a security group has an inbound rule allowing TCP port 443 from 0.0.0.0/0 but HTTPS connections fail, what is the most probable cause?
If a security group has an inbound rule allowing TCP port 443 from 0.0.0.0/0 but HTTPS connections fail, what is the most probable cause?
medium📝 Predict Output Q4 of 15
Step-by-Step Solution
Solution:
Step 1: Confirm Security Group Rule
Inbound TCP port 443 from anywhere is allowed by the security group.Step 2: Check Other Network Controls
Network ACLs can block traffic even if security groups allow it.Step 3: Evaluate Options
Outbound rules missing port 80 do not affect inbound HTTPS (port 443). Source 0.0.0.0/0 is correct for all IPs. HTTP vs HTTPS is unrelated to port 443 blocking.Final Answer:
The instance's network ACL blocks inbound port 443 traffic -> Option BQuick Check:
Network ACLs can override security group permissions [OK]
Quick Trick: Network ACLs can block allowed security group traffic [OK]
Common Mistakes:
- Assuming security group rules are the only firewall
- Confusing inbound and outbound rules
- Misunderstanding source IP notation
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