To capture packets on a Cisco Secure Firewall Threat Defense (formerly Firepower Threat Defense) device and ensure that the MAC address appears in the tcpdump output, you need the following: - Use the -n option to prevent name resolution (makes output clearer). - Use the -e option to include the link-layer header in the output, which shows MAC addresses. - Filter by the source IP address (or host IP). So, the correct tcpdump command should include -ne and a filter for the IP address.