A network technician is troubleshooting a newly installed workstation in a corporate office. The workstation shows an active physical link light on its NIC but cannot access local network resources or the internet. Running `ipconfig /all` on the workstation displays an IPv4 address of with a subnet mask of and no default gateway listed. Running `ping 127.0.0.1` succeeds. Assigning a valid static IP address () manually allows local interface binding, but the client still cannot ping its default gateway (). The switch port is configured with 802.1X port-based access control and assigned to VLAN 20. Which of the following is the MOST likely cause of this connectivity failure?
- The switch port has blocked data traffic because the client workstation failed 802.1X network authentication.Answer
- BThe workstation's network interface card has experienced a hardware failure because APIPA addresses indicate damaged physical circuitry.
- CThe corporate DNS server is offline, preventing the workstation from obtaining a dynamic IP address lease.
- DThe NIC link lights are misleading because a pinout mismatch prevents the TCP/IP stack from processing loopback diagnostics.
Answer
The switch port has blocked data traffic because the client workstation failed 802.1X network authentication.
On networks enforced with IEEE 802.1X port-based Network Access Control (NAC), a switch port stays in an unauthenticated state until the supplicant (client software) successfully authenticates with the authentication server (e.g., RADIUS). In this unauthenticated state, the switch drops all user data traffic (DHCP requests, ICMP pings, ARP requests). Consequently, the client defaults to an APIPA address (). Manually setting a static IP address does not bypass 802.1X port blocking at the switch level.
Step-by-Step Solution
Key Concept
802.1X Port Authentication and Layer 2 Network Access Control Diagnostics
Estimated Time:2m 30s