AWS - Security Groups and Network ACLs
A security group has an inbound rule allowing TCP port 22 from 203.0.113.0/24. A user from IP 203.0.114.5 cannot SSH into the instance. What is the most likely reason?
A security group has an inbound rule allowing TCP port 22 from 203.0.113.0/24. A user from IP 203.0.114.5 cannot SSH into the instance. What is the most likely reason?
medium📝 Debug Q7 of 15
Step-by-Step Solution
Solution:
Step 1: Check CIDR range in inbound rule
The rule allows IPs from 203.0.113.0 to 203.0.113.255 only.Step 2: Compare user's IP
User IP 203.0.114.5 is outside the allowed range, so connection is blocked.Final Answer:
The user's IP is outside the allowed CIDR range -> Option AQuick Check:
IP outside CIDR = blocked [OK]
Quick Trick: CIDR must include user IP to allow access [OK]
Common Mistakes:
MISTAKES- Assuming AWS blocks port 22 by default
- Ignoring outbound rules impact
- Thinking security groups don't control SSH
Master "Security Groups and Network ACLs" in AWS
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