Eccouncil Exam 312-38 Topic 7 Question 3 Discussion

Steven's company has recently grown from 5 employees to over 50. Every workstation has a public IP address and navigated to the Internet with little to no protection. Steven wants to use a firewall. He also wants IP addresses to be private addresses, to prevent public Internet devices direct access to them. What should Steven implement on the firewall to ensure this happens?