A company hires a penetration tester to determine if there are any vulnerabilities in its new VPN concentrator installation with an external IP of 100.170.60.5. Which of the following commands will…

fpipe.exe is a TCP port-forwarding and port-redirecting tool used to tunnel traffic, not to probe or test VPN availability on a remote host.

ike-scan communicates directly over UDP port 500 using the IKE protocol, which is the handshake mechanism for IPsec VPNs. The -A flag tests aggressive mode negotiation, and --sourceip allows spoofing for additional probing - both are standard techniques to determine if a VPN concentrator is alive and accepting IKE negotiations. No other tool in the list speaks the IKE protocol natively.

nmap -sS performs a TCP SYN scan with OS/service detection and packet fragmentation (-f), which tests open TCP ports but cannot probe the UDP-based IKE protocol used by IPsec VPN concentrators.

The nc (netcat) command shown here attempts to open a reverse shell to port 8080 on the target, which is a post-exploitation technique and has nothing to do with testing VPN availability.