A technician is troubleshooting an issue where a wireless client can associate with an access point but cannot obtain an IP address via DHCP. The technician checks the DHCP server and sees no lease requests from the client's MAC address. Which of the following is the most likely cause?
Correct. When the DHCP server is on a different subnet than the wireless clients, the AP or a Layer 3 device must relay DHCP broadcasts. Without a relay, the client's DHCP discover messages never reach the server.
Why this answer
The client can associate with the AP but cannot obtain an IP address, and the DHCP server shows no lease requests from the client's MAC. This indicates that DHCP discovery broadcasts are not reaching the DHCP server, which is common when the client and server are on different subnets and the AP (or a Layer 3 device) is not configured with a DHCP relay (ip helper-address). Without a relay, broadcast DHCP messages are dropped at the router, so the server never sees the request.
Exam trap
The trap here is that candidates often assume the AP automatically forwards DHCP broadcasts to the server, forgetting that broadcast traffic does not cross Layer 3 boundaries without an explicit relay configuration.
How to eliminate wrong answers
Option A is wrong because a faulty wireless adapter would typically prevent association or cause intermittent connectivity, but here the client successfully associates, ruling out hardware failure. Option C is wrong because an incorrect SSID would prevent association entirely, not allow association while blocking DHCP. Option D is wrong because the AP operating on the wrong channel would cause poor signal or inability to associate, but the client has already associated, so channel mismatch is not the issue.