The BIG-IP Administrator configures an HTTP monitor with a specific receive string. The status is marked 'down'. Which tool should the administrator use to identify the problem?

Ping only verifies basic network connectivity using ICMP and cannot diagnose issues related to application-layer HTTP responses or receive strings.

"Health" is a status indicator, not a diagnostic tool that can be used to identify the root cause of a monitor failure.

`tcpdump` allows the administrator to capture and inspect the actual HTTP request sent by the monitor and the corresponding response from the server, which is essential for verifying receive string matches and identifying application-layer problems.

`ifconfig` displays network interface configuration and statistics but does not provide insights into application-layer traffic or HTTP monitor receive string failures.