If users canaccess local network resourcesbut not theinternet, the most likely culprit is amisconfigured or missing default gateway. The default gateway routes traffic from the local network to external networks (i.e., the internet). If it’s not properly set or was altered during a firewall update, internet traffic won’t be forwarded correctly.

Option A:Static IPs could cause conflict, but wouldn't affect only external access if configured correctly.

Option C:An incorrect subnet mask could isolate devices, but local communication would likely be impacted too.

Option D:VLANs segment networks; while misconfigured VLANs could cause access issues, they’d more likely isolate local traffic as well.

CompTIA A+ Core 1 Exam Objective Reference:

Objective 2.6: Given a scenario, configure and troubleshoot network connectivity.