Secure Shell (SSH) is the correct response as it provides a secure channel over an unsecured network, allowing a user to log into another computer over a network, execute commands in a remote machine, and move files from one machine to another. It ensures secure data communication and remote command-line, login, and remote command execution. VPN could potentially allow access to the isolated VLAN if it's configured correctly, but it's more about providing access to the network, not managing devices, and it wouldn’t be a direct access method. RMM is designed for managing systems but lacking direct, low-level access to a network device. The use of RDP and other remote desktop tools is not standard for network device management and would not be applicable for a core switch. VNC operates similarly to RDP and is also not intended for low-level network device management.