Final answer:
The Nmap command-line switch for a full-connect port scan is '-sT', which initiates a TCP connect scan, completing the three-way handshake and being detectable by intrusion systems.
Step-by-step explanation:
The Nmap command-line switch for a full-connect port scan is -sT. When this switch is used, Nmap performs a TCP connect scan, which is the most basic form of TCP scanning. In a full-connect scan, Nmap attempts to establish a full TCP connection with the target machine. This type of scan is thorough but also the most detectable by intrusion detection systems because it completes the three-way handshake process used by TCP to establish a connection.
The Nmap command-line switch for a full-connect port scan is -sT.