A secondary Wireless LAN Controller (WLC) is responsible for registering Lightweight Access Points (LAPs) in the event that the primary controller fails. This ensures that there is no interruption in service for the wireless clients. The secondary WLC acts as a backup, taking over the management of the LAPs and maintaining network stability and connectivity. References: The Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR) course material covers the roles and responsibilities of primary and secondary WLCs in a wireless network infrastructure1.