220-1101 Question 161
Single answerLANA technician is troubleshooting a desktop on a small office LAN. The PC can print to a local USB printer, but it cannot access file shares on other office computers or browse the internet. The link light on the NIC is on. Running ipconfig shows an IPv4 address of 169.254.22.81 with a subnet mask of 255.255.0.0. Other PCs on the same network are using 192.168.10.x addresses and are working normally. Which of the following is the MOST likely cause of the problem?
- A
The PC failed to obtain an IP address from the DHCP server
- B
The PC has a duplicate IP address on the LAN
- C
The default gateway on the PC is incorrectly configured
- D
The switch port is operating at the wrong speed
Show answer and explanation
Correct answer: A
Explanation
This question tests recognition of APIPA behavior in a LAN troubleshooting scenario. In Windows, when DHCP fails and no static IP is configured, the system can assign an Automatic Private IP Addressing address in the 169.254.0.0/16 range. That allows only limited local communication with similarly self-assigned hosts and does not place the computer on the office's intended 192.168.10.0 network. In a real environment, the technician should verify physical connectivity, confirm the DHCP server is reachable, run ipconfig /release and ipconfig /renew, and check for issues with the switch port, VLAN assignment, or DHCP scope availability. This aligns with standard TCP/IP troubleshooting practices and Microsoft documentation on APIPA and DHCP behavior.
- A. Correct.
Correct. An address in the 169.254.0.0/16 range is an APIPA address, which Windows assigns automatically when the host cannot contact a DHCP server and no valid static address is configured. Because the rest of the office is using 192.168.10.x addresses, this PC is not on the same logical network and will be unable to reach local shares or the internet. The active link light shows Layer 1 connectivity is present, making DHCP failure the most likely issue.
- B. Incorrect.
Incorrect. A duplicate IP address typically occurs when two devices are configured with the same valid address on the same subnet. In that case, the PC would usually still show an address in the expected 192.168.10.x range, not a self-assigned 169.254.x.x APIPA address. Duplicate IPs can cause intermittent connectivity, but they do not normally result in APIPA.
- C. Incorrect.
Incorrect. An incorrect default gateway can prevent internet access and access to remote subnets, but it would not typically stop communication with other devices on the same local subnet if the PC had a valid 192.168.10.x address. The APIPA address indicates the problem occurs earlier in the process: the PC does not have a proper LAN IP configuration at all.
- D. Incorrect.
Incorrect. A speed or duplex mismatch can cause poor performance, packet errors, or intermittent connectivity, but it does not cause Windows to self-assign a 169.254.x.x address. Since the NIC link light is on and the symptom specifically points to APIPA, the more direct cause is failure to receive DHCP configuration.