When a user reports that they can no longer access the company's internal web server that was previously accessible, and you suspect that the port might be blocked on the firewall, which of the following is an effective first step in troubleshooting this issue?
Use the telnet command to test access to the port on which the web server should be listening.
Check the email application settings on the user's computer.
Ping the IP address of the web server to see if the server is up and running.
Immediately modify the firewall settings to unblock the suspected port.