What command can be used to display active open Telnet or rlogin connections?

The command used to display active open Telnet or rlogin connections is indeed "Show sessions." This command provides a view of all the current active sessions on a device, allowing an administrator to monitor and manage live connections, including those established through Telnet or rlogin protocols.

In the context of network security and management, understanding active sessions is essential for maintaining security and ensuring that unauthorized connections are detected. By seeing which sessions are currently active, administrators can assess the health of the network, squelch unauthorized access, and manage resources accordingly.

The other choices, while they might seem plausible, do not provide the specific functionality of displaying active connections. For instance, "Show connections" could imply a more general set of connections without focusing on session management, and "Show users" typically lists users currently logged into the system rather than detailing active sessions. "Display sessions," although sounding similar, is not the standard syntax recognized in most command-line interfaces used for these tasks. Thus, the specific command "Show sessions," makes it the accurate choice for this query.