A cable was looped and created a broadcast storm is the most likely explanation for the symptoms of high CPU usage and blinking lights on the switch. A cable loop is a situation where a switch port is connected to another switch port on the same switch or another switch, creating a circular path for network traffic. A cable loop can cause a broadcast storm, which is a network phenomenon where a large number of broadcast or multicast packets are flooded on the network, consuming bandwidth and CPU resources. A broadcast storm can cause network congestion, performance degradation, or failure. A cable loop can occur when an employee rearranges the wiring closet without proper documentation or verification. A cable loop can be prevented or detected by using Spanning Tree Protocol (STP) or loop detection features on the switch. Reference: [CompTIA Network+ Certification Exam Objectives], What Is a Broadcast Storm? | Definition & Examples | Forcepoint

Explanation
The technician was identifying the problem by gathering information with this note. This is the first step of the troubleshooting methodology, which is a systematic process of finding and resolving issues in a network or system. By gathering information, the technician can understand the symptoms, scope, and impact of the problem, as well as collect relevant data from various sources, such as users, logs, tools, or documentation.
The note shows that the technician was asking questions to the user, checking the network status and configuration, and reviewing previous tickets to gather information about the problem. References: [CompTIA Network+ Certification Exam Objectives], Troubleshooting Methodology - CompTIA Network+ N10-007 -
1.4 | Professor Messer IT Certification Training Courses

A software-defined network (SDN) is a network architecture that decouples the control plane from the data plane and centralizes the network intelligence in a software controller. The control plane is the part of the network that makes decisions about how to route traffic, while the data plane is the part of the network that forwards traffic based on the control plane's instructions. The control layer is the layer in an SDN that contains the controller and the routing protocols that communicate with the network devices. The control layer is responsible for managing and configuring the network devices and providing them with the necessary information to forward traffic. Reference: https://www.comptia.org/training/books/network-n10-008-study-guide (page 378)