Final answer:
It is NOT possible to enable Layer 2 security on a Cloud-based AP, whereas Autonomous, Lightweight, and Embedded APs generally support such security features. The limitations of enabling Layer 2 security on a Cloud-based AP are due to the remote internet-based cloud management services which may not support direct configuration.
Step-by-step explanation:
The question is asking about when it is NOT possible to enable Layer 2 security on a wireless local area network (LAN). The different options provided are various types of access points (APs) that are used in creating a WLAN. Layer 2 security refers to security measures implemented at the data link layer of the OSI model. While this type of security can typically be implemented on most access points, there might be limitations based on how the AP is managed or controlled.
An Autonomous AP is managed individually and can have Layer 2 security settings applied directly to it. A Lightweight AP is controlled by a wireless LAN controller; the security settings are primarily managed through the controller, but Layer 2 security is still possible. An Embedded AP, which is built into devices such as routers or range extenders, generally supports Layer 2 security as well. However, a Cloud-based AP is managed remotely over the internet using cloud services, and depending on the service provider and the cloud management architecture, it may not support direct Layer 2 security configuration.