5.4 Troubleshooting Tools
Basic Network Device Commands
📘CompTIA Network+ (N10-009)
What is the show power command?
The show power command is used on network devices, especially switches (mainly Cisco switches), to check the power status of the device and any connected components, such as PoE (Power over Ethernet) devices.
- PoE devices are devices like IP phones, access points, and security cameras that get both network connection and power from the network switch.
- The command helps IT staff verify if the switch is supplying enough power to connected devices and troubleshoot power-related problems.
Why is it important?
- Check PoE status: You can see which ports are supplying power to devices.
- Prevent overloads: It tells you if the switch is exceeding its power budget.
- Troubleshooting: If a device isn’t working, you can see if it’s not getting power from the switch.
- Device health: Helps ensure critical devices like phones and access points stay powered.
Where is it used?
- On a switch CLI (Command-Line Interface) in IT networks.
- Example scenario in IT:
- A Wi-Fi access point suddenly stops working. Running
show powercan reveal if the switch port lost PoE or if the switch has run out of power to allocate.
- A Wi-Fi access point suddenly stops working. Running
Typical show power output
The exact output may vary depending on the switch model, but usually it includes:
| Field | Description |
|---|---|
| Port | The physical port on the switch (e.g., FastEthernet0/1, GigabitEthernet1/0/1) |
| Device | Type of device connected (IP phone, access point, etc.) |
| Class | PoE class of the device (0–4) |
| Status | Shows if the port is delivering power (on/off) |
| Power (Watts) | How much power is being supplied to the device |
| Allocated Power | Total power budget being used |
| Available Power | Remaining PoE power the switch can provide |
Example show power output
Switch# show power
Port Device Class Status Power(W)
Gi1/0/1 IP Phone 2 On 7.5
Gi1/0/2 Access Point 4 On 15.4
Gi1/0/3 Unused - Off 0
-----------------------------------------------
Total Allocated Power: 22.9W
Available Power: 77.1W
Explanation:
- Gi1/0/1 is powering an IP Phone at 7.5W.
- Gi1/0/2 is powering a Wi-Fi Access Point at 15.4W.
- Gi1/0/3 has no device connected, so no power is being used.
- The switch has a total budget, and it shows how much is already allocated and how much is still available.
Useful variations of the command
Some network devices have extended options:
show power inline– Displays only the PoE-enabled ports and their power usage.show power detail– Shows detailed statistics, including power supply health, temperature, and any errors.show power inline police– Displays PoE policy violations, like devices trying to draw too much power.
Key points for the CompTIA Network+ exam
- Purpose: Verify power supply and PoE status of network devices.
- Where used: Switches, mostly for PoE devices like IP phones, APs, cameras.
- Important for troubleshooting:
- Device not powering on → check PoE status.
- Switch not supplying enough power → check total available power and allocation.
- Understanding output: Know the fields like port, device type, status, and power in watts.
- Common related commands:
show interface→ Check link and operational status.show vlan→ Verify VLAN assignment of PoE devices if network connectivity issues occur.
✅ Exam tip:
The CompTIA exam may ask what command to use to check if a switch is powering devices or how to troubleshoot PoE issues. The correct answer is show power or show power inline depending on the wording.
