User's Manual

Chapter 3: Troubleshooting

Powered Device Not Receiving Power

Problem: Port’s PoE LED is OFF

Solutions: If a powered device (PD) is not receiving power from the

AT-GS900/8PS switch and the port’s PoE LED is off, do the following:

 Verify that the AT-GS900/8PS is has AC power and the Power

LED is on.

 Verify that the port’s link L/A LED is either solid or blinking green. If

the L/A LED is off, do the following:

- Check the Ethernet connections between the AT-GS900/8PS

port and the powered device.

- For legacy PDs, check to be sure that it is designed to receive

power over pins 1, 2, 3, and 6 on the RJ-45 port. This can be

verified by reviewing the device’s documentation or data sheet.

If it is not capable of receiving power on these pairs, it is

incompatible with the AT-GS900/8PS.

Note

For an explanation of the PoE Guard Band, see “PoE Port

Prioritization” on page 27.

Problem: Port POE Status LED is Blinking

If the Port PoE Status LED is blinking, it indicates one of the following

problems:

 There may be a short circuit in the Ethernet cable. You can verify

that the Ethernet cable does not have a short by replacing it with a

cable that you know is good. If the problem is resolved with the

good cable, then the original cable has a fault.

 The power demand of the PD may be overloading the port. Check

that the device’s power requirements does not exceed 30 W. This

can be verified by reviewing the device’s documentation or data

sheet. The demand for PoE power from the power device

connected to the port is greater than 30 W. The maximum amount

of power any port can supply by itself is 30 W. More than 30 W

exceeds the port’s ability to deliver PoE power.

 The total demand for PoE power on all ports is exceeding the 75 W

maximum PoE power limit of the switch. This condition occurs

when you connect an additional power device to a switch port and

the switch attempts to deliver more than the maximum PoE power

limit for the switch. When this situation occurs, the lowest priority

port(s) is denied PoE power so the combined PoE power delivered

to all of the power devices remains under 75 W.