Struggling with a Cisco IP phone that isn’t powering up via PoE? Learn why checking the PoE settings on the switch port should be your first troubleshooting step for the Cisco Certified Field Technician (CCT) exam.
Table of Contents
Question
A technician is troubleshooting a Cisco IP phone that is not receiving power. The switch supports PoE. What should be checked first?
A. Power injector connection
B. DHCP server settings
C. PoE settings on the switch port
D. TFTP server availability
E. Phone firmware version
Answer
C. PoE settings on the switch port
Explanation
If the switch supports Power over Ethernet (PoE) but the phone is not powering on, the PoE configuration on the switch should be checked to ensure it is enabled.
When a Cisco IP phone is not receiving power from a switch that supports Power over Ethernet (PoE), the primary factor to check is the PoE configuration on the specific switch port.
PoE Settings on the Switch Port
The switch may support PoE, but individual ports can have PoE functionality disabled or misconfigured. Use the show power inline command to verify if PoE is enabled and if sufficient power is being supplied to the port. The configuration mode command power inline auto ensures the port automatically detects and powers connected devices like IP phones. If the port is set to power inline never, PoE is disabled for that port, and the phone will not receive power.
Why Not Other Options?
Power injector connection: Only relevant if the switch does not support PoE or if a midspan injector is used, which is not the case here.
DHCP server settings: DHCP is necessary for IP address assignment, not for power delivery.
TFTP server availability: TFTP is used for firmware and configuration file downloads, not for power.
Phone firmware version: Outdated firmware may cause operational issues, but it does not affect PoE power delivery.
Key Troubleshooting Steps
- Confirm the switch port is not administratively shut down or error-disabled using show interface status.
- Check that the port is configured for PoE (power inline auto) and not disabled (power inline never).
- Ensure the switch’s overall PoE power budget is not depleted, which can prevent devices from powering up.
Ensuring the correct PoE configuration on the switch port is the essential first step when a Cisco IP phone is not receiving power from a PoE-capable switch
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