In several networking environments of fit AP+AC, how do APs register?

In several networking environments of fit AP+AC, how do APs register?

No matter what kind of networking environment, manual registration and automatic registration can be used. 

(1) Direct mode is the same as Layer 2 mode. The management addresses of AC and AP are in the same network segment, and AP can initiate a layer 2 broadcast request to find and register with AC. 

(2) In the layer 3 mode, because the AP needs to know the AC address to register, but the AC address cannot be obtained for the layer 2 broadcast request. The only way is configuring the OPTION 43 field in the DHCP server, and load the AC address into DHCP DFFER message. The AP knows the address of the AC while automatically obtaining the IP address.There is another way, that is, using DNS whose configuration is relatively complicated. Generally, OPTION 43 is used for deployment.