A Security Engineer has been asked to troubleshoot inbound connectivity to a web server. This single web server is not receiving inbound connections from the internet, whereas all other web servers are functioning properly.
The architecture includes network ACLs, security groups, and a virtual security appliance. In addition, the Development team has implemented Application Load Balancers (ALBs) to distribute the load across all web servers. It is a requirement that traffic between the web servers and the internet flow through the virtual security appliance.
The Security Engineer has verified the following:
1. The rule set in the Security Groups is correct
2. The rule set in the network ACLs is correct
3. The rule set in the virtual appliance is correct
Which of the following are other valid items to troubleshoot in this scenario? (Choose two.)
A. Verify that the 0.0.0.0/0 route in the route table for the web server subnet points to a NAT gateway.
B. Verify which Security Group is applied to the particular web server’s elastic network interface (ENI).
C. Verify that the 0.0.0.0/0 route in the route table for the web server subnet points to the virtual security appliance.
D. Verify the registered targets in the ALB.
E. Verify that the 0.0.0.0/0 route in the public subnet points to a NAT gateway.
Web servers are behind an ALB, and likely share a subnet-level routing table, so A and C are wrong. E doesn’t help for inbound connections to the web servers. Answer therefore B and D.
Not A, Not E – NAT Gtwy – applies only to outbound, the issue is “not receiving inbound connections”
Same with C – "0.0.0.0/0 route in the route table for the web server subnet points to the virtual security appliance" – sounds like an outbound rule.
So yes B and D