If a computer can access internal network resources but cannot reach external websites, the most likely issue is a DNS configuration problem. According to CompTIA Core 1 (220-1201) networking troubleshooting methodology, DNS should be one of the first items checked when internet access fails but local connectivity remains intact.
DNS translates human-readable domain names into IP addresses. If DNS settings are incorrect, missing, or pointing to an invalid server, the computer will be unable to resolve website names even though it has network connectivity. Since other users on the same network can access the internet, the issue is isolated to the individual workstation.
Replacing the network cable is unnecessary because internal connectivity is already working. Restarting the DHCP server would impact all users, not just one. Adjusting firewall rules on the router would affect the entire network rather than a single computer.
CompTIA emphasizes starting with least disruptive and most likely causes when troubleshooting. Verifying DNS settings aligns with this best-practice approach.
References:CompTIA A+ Core 1 (220-1201) Official Study Guide - Network Troubleshooting and DNS