A system administrator tests an externally reachable web server from outside the corporate firewall. After provisioning multiple VMs behind NAT, they can no longer reach the web server. Which component could be responsible for blocking access?

A system administrator tests an externally reachable web server from outside the corporate firewall. After provisioning multiple VMs behind NAT, they can no longer reach the web server. Which component could be responsible for blocking access?

• A. Intrusion Prevention System
• B. Blacklisting
• C. Intrusion Detection System
• D. Firewall

Answer: (D)

The boundary control at the network edge is what’s stopping the connection. A firewall sits where the corporate network meets the Internet and enforces which inbound traffic is allowed to reach internal hosts. When you place multiple VMs behind NAT, inbound requests from outside must be properly forwarded to the internal web server (via port forwarding or equivalent rules). If those firewall/NAT rules aren’t configured correctly, the firewall will drop the traffic before it gets to the server, blocking access. IDS and IPS monitor or block traffic based on security detections, but they’re not typically the default reason normal external access to a behind-NAT server would be blocked. Blacklisting could block specific IPs, but that wouldn’t explain a general NAT-related reachability issue. So the firewall is the most plausible blocker.

The boundary control at the network edge is what’s stopping the connection. A firewall sits where the corporate network meets the Internet and enforces which inbound traffic is allowed to reach internal hosts. When you place multiple VMs behind NAT, inbound requests from outside must be properly forwarded to the internal web server (via port forwarding or equivalent rules). If those firewall/NAT rules aren’t configured correctly, the firewall will drop the traffic before it gets to the server, blocking access. IDS and IPS monitor or block traffic based on security detections, but they’re not typically the default reason normal external access to a behind-NAT server would be blocked. Blacklisting could block specific IPs, but that wouldn’t explain a general NAT-related reachability issue. So the firewall is the most plausible blocker.