A network technician is working on a PC with a faulty NIC.

If a switch has port security enabled (such as sticky MAC or a configured allowed MAC), the port will only allow the original NIC’s MAC address. When a new NIC with a different MAC address is installed, the port rejects traffic, preventing network connectivity.

B. BPDU guard protects against rogue switches, not end hosts.

C. Link aggregation applies when bundling multiple uplinks, not a single PC connection.

D. PoE budget applies to powered devices like APs, not PCs.

References (CompTIA Network+ N10-009):

Domain: Network Troubleshooting — Port security, MAC address filtering, switch security features.