Notifications are the lowest logging level and will provide the desired information regarding switch port up/down activity. According to the CompTIA Network+ Study Manual, notifications "are used for logging normal activities, such as port up/down events, link changes, and link flaps."

It is most likely that the issue is caused by port security, as this is a feature that can prevent new devices from connecting to the LAN. Port tagging, port aggregation, and port mirroring are all features that are used to manage traffic on the network, but they are not related to the connectivity of new devices. If the technician has configured port security on the network and the new PC does not meet the security requirements, it will not be able to connect to the LAN.

The data link and network layers are responsible for handling packets from the source to the destination and checking for errors. The data link layer is the second layer of the OSI model, which is a conceptual framework that describes how different network functions are organized and interact. The data link layer is responsible for providing reliable and efficient data transmission between two adjacent nodes on a network. The data link layer uses frames as its unit of data, and adds a header and a trailer to each frame that contain information such as source and destination MAC addresses, frame type, and error detection code. The data link layer can check for errors by using techniques such as parity check, checksum, or cyclic redundancy check (CRC). The network layer is the third layer of the OSI model, which is responsible for providing logical addressing and routing of packets across different networks. The network layer uses packets as its unit of data, and adds a header to each packet that contains information such as source and destination IP addresses, protocol type, and hop count. The network layer can check for errors by using techniques such as Internet Control Message Protocol (ICMP), which can send and receive error messages or diagnostic information. Reference: [CompTIA Network+ Certification Exam Objectives], Data Link Layer - an overview | ScienceDirect Topics, Network Layer - an overview | ScienceDirect Topics