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Issue:
PoE power fault errors occur on FortiSwitch-148F-FPOE v7.0.4 build0071 using PoE Firmware Version 2.2.3.
User-Impact:
PoE-powered devices (PDs) such as IP Phones or Access Points connecting to FortiSwitch-PoE ports do not power on.
Prerequisite check: Cable diagnostics.
Summary:
FortiSwitch shows the following PoE power fault errors in the command outputs below:
get switch poe inline
diagnose switch poe status <Port_ID>
Power Fault: Error Type 38 (Port is off: Discharged load)
Power Fault: Error Type 36 (Port is off: Voltage injection into the port)
Cause:
When the FortiSwitch-PoE port is connected to a PSE (Power Sourcing Equipment) such as a 3rd party PoE Switch, the 3rd party PoE Switch may inject power into the FortiSwitch port. This causes the PoE errors 'Discharged load' and 'Voltage injection into the port', which may harm the device.
Fix:
- Run the cable diagnostic command on all ports, one by one, to detect if a port is in a 'short' state, and solve this state before following further steps:
diagnose switch physical-ports cable-diag <port_name>
- Disable 'poe-pre-standard-detection' if it's not in use:
The purpose of 'poe-pre-standard-detection' (also called legacy detection or capacitor detection) is to support old PDs like the Cisco 794x phone released decades ago. If the network administrator does not have these kinds of old PDs or similar devices, then pre-standard detection should be kept disabled by default.
There was a bug in v7.0.3 GA where 'poe-pre-standard-detection' was always enabled. This issue has been fixed on FortiSwitch OS v7.0.4 GA. From v7.0.4 and newer versions, 'poe-pre-standard-detection' is now disabled by default.
FortiGate CLI (for Managed FortiSwitches):
config switch-controller managed-switch
edit <FortiSwitch_serial_number>
set poe-pre-standard-detection disable
next
end
FortiSwitch CLI (For Standalone FortiSwitches):
config switch global
show full
set poe-pre-standard-detect disable
end
- Disable PoE status on the 3rd party PoE Switch or FortiSwitch that's plugged/connected into the FortiSwitch port:
FortiGate CLI (For Managed FortiSwitch units):
config switch-controller managed-switch
edit <FortiSwitch_serial_number>
config ports
edit <port_name>
set poe-status disable
end
end
FortiSwitch CLI (For Standalone FortiSwitch units):
config switch physical-port
edit <port
set poe-status disable
end
Refer to this KB article to disable POE on Managed FortiSwitches inter-switch links: Technical Tip: How to Disable PoE on FortiLink Ports.
- Power-cycle the affected FortiSwitch using the below command if the PoE error does not go away:
execute reboot
Note:
To avoid loss of configuration settings, download a backup of the FortiSwitch configuration before attempting a reboot.
See Page 77 of FortiSwitch 6.4.5 - Managed by FortiOS 6.4 for more information:
- If error 36 and error 38 are gone after a reboot, the issue is fixed.
- If error 36 and error 38 are still present, log a ticket with Fortinet Support with the affected FortiSwitch Serial Number.
- If this PoE error is occurring between two adjacent/interconnected FortiSwitches, attach the following outputs from both FortiSwitches to the ticket for further analysis:
get hardware status
get switch poe inline
diagnose switch poe status <Port_ID>
show full-configuration switch interface
show full-configuration system interface
show full
diagnose debug report
Related article:
Troubleshooting Tip: Diagnosing a PoE fault on a FortiSwitch.
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