Which TLV value must be included in DHCP Option 43 to ensure APs join the WLC?

The correct TLV value is 0xf1. This is the standard vendor-specific TLV type for Cisco Lightweight Access Point (LAP) discovery in DHCP Option 43. When an AP receives a DHCP response with Option 43 containing 0xf1, it interprets the subsequent data as the IP address(es) of the Wireless LAN Controller (WLC) it should join. 0x77 is an incorrect hexadecimal value and not used for this purpose. "AAA" is a string and not a valid TLV value. 642 is a decimal number and not the correct hexadecimal TLV for WLC discovery.