I just replaced the old HP ProCurve switch with a new Cisco SG 300-28P managed switch. It has PoE on all ports. Everything works, except for my domain server that went offline and the network interface appears to be dead. Windows says the network cable is disconnected, and no lights blink on the switch. Tried different cables and different ports on the switch.

The Cisco PoE ports are supposed to be auto-sensing, i.e. not to send power to a device that cannot handle it. Is this technique not 100% reliable? The server is a SHUTTLE XS35V2 with an onboard network chip, so it is probably fried.

My questions:

• is this plausible?
• who's fault is it - Shuttle or Cisco (i.e. which support line should I try first)?

UPDATE: I did go back and tried another switch between the server and the Cisco switch, and indeed, the connection came back to live. When everything is powered down and I start fresh, with the server connected to the Cisco switch, the port light will blink for a while and the connection status is "No Internet connection" at first until it goes off after about 20 seconds and the connection status changes to "Network cable disconnected". On the other switch it works. Clearly not a PoE issue now. I will start looking into the Cisco's onboard diagnostic functions, but so far I have not noticed anything unusual in the log.