220-1101 Question 142
Single answerInternet Protocol (IP) addressingA technician is troubleshooting a Windows laptop that cannot access file shares or the internet after being moved to a different office. The laptop's network settings show the following IPv4 configuration: IP address 169.254.22.18, subnet mask 255.255.0.0, default gateway blank. Other computers in the office are using addresses in the 192.168.10.0/24 network and can access network resources normally. Which of the following is the MOST likely cause of the problem?
- A
The laptop failed to obtain an address from the DHCP server and assigned itself an APIPA address
- B
The laptop has a valid static IP address for the local subnet, but the DNS server is offline
- C
The default gateway on the laptop is incorrectly configured for IPv6 instead of IPv4
- D
The laptop is using the correct IPv4 network, but the subnet mask should be 255.255.255.128
Show answer and explanation
Correct answer: A
Explanation
This question tests practical identification of IPv4 addressing problems. In a normal office LAN using 192.168.10.0/24, a host showing 169.254.x.x with a 255.255.0.0 mask and no default gateway strongly indicates APIPA. APIPA is a link-local addressing mechanism used by Windows when DHCP fails. Systems with APIPA addresses can communicate only with other devices on the same local link that also have 169.254.x.x addresses, and they typically cannot reach routers, file shares on a different subnet, or the internet. Best practice is to verify physical connectivity, confirm the NIC is enabled, renew the DHCP lease, and check switch, VLAN, or DHCP server availability. This behavior is consistent with Microsoft documentation on Automatic Private IP Addressing and standard TCP/IP troubleshooting practices covered in CompTIA A+ Core 1 objectives.
- A. Correct.
Correct. An address in the 169.254.0.0/16 range is an Automatic Private IP Addressing (APIPA) address. Windows assigns this address when the client is configured for DHCP but cannot reach a DHCP server to obtain a valid lease. Because the laptop is on a network where other systems are using 192.168.10.0/24 and have normal connectivity, the most likely issue is failure to communicate with DHCP, such as a bad cable, disabled switch port, wireless VLAN mismatch, or DHCP service/path problem.
- B. Incorrect.
Incorrect. A valid static address for this subnet would need to be in the 192.168.10.0/24 range, not 169.254.22.18. Also, DNS issues typically prevent name resolution but do not usually prevent all local IP communication if the client has a valid address and gateway. The displayed address already indicates a more fundamental addressing problem.
- C. Incorrect.
Incorrect. The primary issue is that the laptop does not have a valid IPv4 address or default gateway for the office network. Even if IPv6 settings were present, the APIPA address in IPv4 clearly shows the device did not receive proper IPv4 configuration. This option distracts by focusing on gateway settings when the absence of a valid leased address is the first problem to fix.
- D. Incorrect.
Incorrect. The laptop is not using the correct IPv4 network. A 192.168.10.0/24 network uses addresses from 192.168.10.1 through 192.168.10.254 for hosts, while 169.254.22.18 is self-assigned and outside that network. Changing the subnet mask to 255.255.255.128 would split a 192.168.10.0 network into two smaller subnets, but it would not explain or correct an APIPA address.