Your company has several small branch offices around the country, but you work as a network administrator at the centralized headquarters building. You need the capability of being able to remotely access any of the remote site's routers to configure them without having to fly to each location in person. Your company's CIO is worried that allowing remote access could allow an attacker to gain administrative access to the company's network devices. Which of the following is the MOST secure way to prevent this from occurring while still allowing you to access the devices remotely?