What is the value used to record the Network Allocation Vector (NAV) in an 802.11 frame?

If a WLAN network fails, engineer A needs to locate the fault. Which of he following fault location process is correct?
1. Check if the air interface signal is normal.
2. Check if the AC and uplink are normal.
3. Check if the AP is working properly.
4. Check if the terminal service is normal.
5. Check if the intermediate network device is working properly.

According to the following configuration example, which of the following is true?
[AC] dhcp enable
[AC] interface VLANif100
[AC-VLANif100] ip address 10.1.100.1 24
[AC-VLANif100] dhcp select interface
[AC-VLANif100] quit

What are the reasons why APs cannot go online (Select 3 Answers)?

What are the conditions for roaming switching triggers generally? (Multiple Choice)