Solving Hardware Problems 57
■ Auto-negotiation settings are the same at both ends. 
Auto-negotiation problems will occur with 10BASE-T or 100BASE-T 
where auto-negotiation is disabled and incorrect cables are being used 
(cross-over or straight)
Auto-negotiation problems will occur with fiber if:
■ The Receiver (RX) and Transceiver (TX) cable connectors are 
swapped
■ Fibers are broken
■ Auto-negotiation differs at either end (a link appears at the ‘fixed’ 
end and not at the auto-negotiation end)
The Unit LED is flashing green
The Switch unit physically forms a stack with other Switch 4400 units, but 
cannot be managed as part of that stack because one or more units have 
not been upgraded to software version 2.0 or later. You must upgrade 
each unit in the stack to this software version, which is available on the 
CD-ROM that accompanies your Switch.
Port LED Status LED flashing yellow
The Switch has a Power over Ethernet (PoE) error. You must press the LED 
Mode button to see which ports are affected and to see whether it is a 
fault or a power budget issue. If there is a fault, then the Packet LED of 
the affected port will be yellow, if a port exceeds its power limit, then the 
Packet LED of the port will flash green. If a port has a PoE POST error then 
the Port LED Status LED of the affected port will flash yellow.
Solving Hardware 
Problems
In the rare event of your Switch unit experiencing a hardware failure, 
refer to the list of suggested solutions below.
An expansion module is installed and the unit will not power up
Ensure that the expansion module is fully seated in the slot and the 
connectors are engaged so that the securing screws can be tightened.
A fan failure warning message is received
Your Switch has a fan monitoring system that will generate fan failure 
warning messages. Fan failure could potentially reduce the lifetime of the 
DUA1720-3AAA05.book  Page 57  Friday, March 7, 2003  11:53 AM