Refer to the exhibit. A network engineer attempts to connect to the Router1 console port. Which configuration is needed to allow Telnet connections?

The `line vty 0 15` command puts the router into configuration mode for the virtual terminal lines, which are specifically designed to accept incoming network-based connections like Telnet and SSH, thus enabling remote access to the router.

The `telnet client` command is used to initiate a Telnet connection *from* the router to another network device, not to enable incoming Telnet connections *to* the router.

The `line console 0` command configures the direct, physical console port, which is used for local serial access and not for remote network-based Telnet connections.

An Access Control List (ACL) entry like `access-list 100 permit tcp any any eq telnet` controls which Telnet traffic is allowed or denied, but it does not enable the Telnet service itself on the router; the VTY lines must first be configured to accept Telnet connections.