220-1101 Question 63
Single answer67/68 – Dynamic Host Configuration Protocol (DHCP)A technician is troubleshooting a user's Windows laptop that cannot access network resources after being moved to a different office. The laptop shows an IP address of 169.254.23.18 with a 255.255.0.0 subnet mask. Other users in the same office are working normally. The technician confirms the network cable is connected and the switch port shows link activity. Which action should the technician perform FIRST to restore connectivity if the issue is related to DHCP?
- A
Configure a static IP address, subnet mask, gateway, and DNS server on the laptop
- B
Run ipconfig /release followed by ipconfig /renew on the laptop
- C
Replace the switch because the port is not passing DHCP traffic
- D
Assign the laptop an APIPA address in the correct range for the office
Show answer and explanation
Correct answer: B
Explanation
The key clue is the 169.254.23.18 address with a 255.255.0.0 mask, which identifies an APIPA assignment. In IPv4 networking, APIPA is used by a host when it cannot contact a DHCP server to obtain a lease. DHCP uses UDP port 67 on the server side and UDP port 68 on the client side. Because the cable is connected, the switch port has link, and other users are working, the most appropriate first step is to renew the DHCP lease from the client with ipconfig /release and ipconfig /renew. If renewal fails, additional steps could include checking the NIC settings, verifying the DHCP scope, testing the cable, or confirming VLAN placement. This aligns with common Microsoft Windows TCP/IP troubleshooting practices and standard CompTIA A+ networking objectives regarding DHCP and APIPA behavior.
- A. Incorrect.
This is not the best first step. While a static configuration might temporarily restore access if the correct settings are known, it bypasses DHCP rather than troubleshooting it. On an A+ scenario, the first action for a client with an Automatic Private IP Addressing (APIPA) address is typically to attempt to obtain a valid lease from the DHCP server.
- B. Correct.
This is correct. A 169.254.x.x address indicates the laptop self-assigned an APIPA address because it did not receive a DHCP lease. Running ipconfig /release and ipconfig /renew forces the client to discard any current lease information and request a new IPv4 address from the DHCP server over UDP ports 67 and 68. This is the appropriate first client-side troubleshooting step when physical connectivity appears to be present.
- C. Incorrect.
This is incorrect because the switch is less likely to be the issue when the port has link activity and other users in the same office are functioning normally. DHCP failure on a single workstation more often points to a client-side lease issue, NIC configuration problem, or local connectivity problem rather than immediate switch replacement.
- D. Incorrect.
This is incorrect because APIPA addresses are automatically self-assigned by the operating system when DHCP fails; technicians do not manually assign them for normal network access. An APIPA address allows only limited local-link communication and will not provide proper connectivity to routed network resources, gateways, or DNS services in a typical office environment.