In a dual-link backup network, what do the APs use to distinguish between the primary AC and the standby AC (Select 3 Answers)?

Wireless users with the same user VLAN and the same SSID can access the Internet, but they can't access each other.
What could be the cause of this phenomenon?

Which command is used by Huawei AC to view information about online access users?

An engineer received a customer complaint, the signal in the room was not good. The engineer suspected that the channel interference was serious. Use the following command to view the AP RF information in the room and get the following output. Which of the following statement is wrong?
[[AC6605] display radio ap-id 0
CH/BW: Channel/Bandwidth
CE: Current EIRP (dBm)
ME: Max EIRP (dBm)
CU: Channel utilization
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AP ID Name RfID Band Type Status CH/BW CE/ME STA CU
0 ap-2 0 2.4G bgn on 1/20M 27/27 0 31%
0 ap-2 0 5G an on 149/20M 28/28 0 2%
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Total: 2

What are the prerequisites for users to achieve three-layer roaming? (Multiple choice)