Huawei ' s HCIA-Datacom WLAN troubleshooting material identifies several causes of wireless station access failures.
Option A is correct because excessive channel utilization causes contention, retransmissions, and degraded wireless communication. The training material indicates that channel utilization exceeding approximately 85% can prevent STAs from accessing the network reliably.
Option B is correct because the WAC can deny wireless client access through blacklist-based admission control.
Option C is correct because network faults may prevent DHCP messages from reaching their destination, leaving the STA without a valid IP address and preventing successful network connectivity.
Option D is correct because a defective wireless network adapter can prevent the STA from establishing or maintaining wireless communication.
Troubleshooting should distinguish failures during scanning, authentication, association, and IP address allocation.
Therefore, all four options represent possible causes.
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