220-1101 Question 140
Single answerPhysical media access control (MAC) addressA small office uses MAC address filtering on its wireless router to allow only approved devices onto the Wi-Fi network. After replacing an employee's laptop, a technician confirms the SSID and WPA2 password are correct, but the new laptop still cannot connect to the wireless network. Other employees can connect without issue. Which action should the technician take NEXT to resolve the problem?
- A
Add the new laptop's wireless adapter MAC address to the router's allow list
- B
Change the new laptop's IP address to match the old laptop's previous address
- C
Reinstall the wireless network driver on the router
- D
Disable DHCP on the new laptop and assign a static gateway
Show answer and explanation
Correct answer: A
Explanation
This scenario tests practical understanding of MAC addresses in a real support situation. A MAC address is a Layer 2 hardware identifier assigned to a network interface, and wireless access points or routers can use MAC filtering to permit or deny association based on that address. When a device is replaced, even if the user, SSID, and Wi-Fi password remain the same, the network interface typically has a different MAC address. As a result, the new device must be added to the allow list. This reflects common SOHO router behavior and aligns with standard networking concepts documented by networking vendors and in IEEE 802 networking practices. IP addressing, DHCP, and gateway configuration occur after the device has been permitted to connect, so they would not fix a MAC-based access control problem.
- A. Correct.
Correct. MAC address filtering allows or blocks devices based on the unique hardware address of the network interface. Because the laptop was replaced, its wireless adapter has a different MAC address than the old system. The technician should add the new wireless NIC's MAC address to the router's approved list so the device can associate with the network.
- B. Incorrect.
Incorrect. IP addressing occurs after the device is allowed onto the network and does not bypass MAC filtering. Matching the old laptop's IP address would not help if the router is blocking the new wireless adapter's MAC address.
- C. Incorrect.
Incorrect. A router does not use a client-side wireless driver in the way a laptop does, so 'reinstalling the wireless network driver on the router' is not an appropriate or realistic fix. The issue described points to access control, not a router driver problem.
- D. Incorrect.
Incorrect. DHCP settings and static gateway configuration relate to Layer 3 addressing after network access is granted. If MAC filtering is denying the laptop at Layer 2, changing DHCP behavior on the client will not resolve the connection issue.