No Network Connectivity When POE (Power Over Ethernet) Sensing Equipment Is Installed

Why did my Device Server lose network connectivity when I installed POE (Power Over Ethernet) sensing equipment?


The POE specification allows for transmission of power over data lines (1,3,2,6) or spare lines (4,5,7,8). It is the responsibility of the POE switch to detect whether a connected device is a PD (Powered Device) or not and accommodate either configuration. It is required of the switch to not put any power signals on the data lines or spare lines if the device it detects is not a PD and does not support POE.

 

This problem is due to negotiations between the Device Server and many different POE switches. The Lantronix 10 baseT Device Server design predates the POE standard and therefore does not support POE.

 

It appears that many POE devices assume POE equipment is connected and do not block the test power signal from the data lines. This will cause noise on the data lines that result in an unreliable Ethernet connection.

 

To determine if the problem is due to the POE switch suppying poser to a non-POE device, remove the POE switch and check to see if ethernet connectivity is restored. 

 

Another test is to add length (approx. 50 feet) to the Ethernet cable. This will dissipate any low power signal and may clear this condition.

 

If ethernet connectivity is restored after performing the tests above then the POE switch is not correctly detecting a non-POE device.  Please check your POE equipment user manual for options to disable POE signals on a specific port.



[Originally Published On: 09/05/2006 06:16 AM]