Faulty Cabling or Connectors Intermittent connectivity or power issues. Devices not detected by the PoE switch. In a basic PoE power supply system, the major components are the power sourcing equipment (PSE), the powered device (PD), and the PoE cables. However, when PoE fails, it can disable critical infrastructure like IP phones, wireless access points, and security cameras. This guide provides a step-by-step troubleshooting. This document describes how to troubleshoot Power over Ethernet (PoE) on Catalyst 9000 PoE-capable switching platforms.