Approximately 1/3 of the access switches at our central office are model WS-C3550-24PWR-SMI switches. We have recently started purchasing the new 7961G-GE phones and it appears through testing that the new phones do not work with the 3550 switches. Watching the logs on the 3550 show that PoE is granted to the device, and the phone does appear to start booting up (speaker button lights, then all buttons light, then the speaker button), and the phone continues to cycle this way but there is never any display on the LCD. The switch logs indicate that PoE was granted but the line protocol never came up. If I connect the 7961 to a 10\100 3560PoE the phone boots normally. I have tested the phones on many different 3550 switches, all with the same result. We are running IOS v12.2(25)SEE2 on all the 3550s. Could this be a bug or is this by design?
Unfortunately the 3550 - 24 PWR only supports Cisco prestandard PoE and the 7961G-GE requires IEEE 802.3af PoE . Here are a few reference docs with this note;
Cisco PoE Product Snapshot
24 10/100 Cisco prestandard PoE ports and 2 GBIC-based Gigabit Ethernet slots
Cisco Catalyst 3550 24 PWR (Cisco prestandard PoE only)
Q. What IP phone models support the IEEE standard method of powered device detection?
A. These Cisco IP phones support IEEE 802.3af PoE:
From this new doc;
Power over Ethernet (PoE) Power Requirements FAQ
Hope this helps! (I know its a bummer :(
Edit: Mahesh, you must slow down for me to keep up :) My typing skills are zero!
The reason 7961G-GE phone does not work with 3550 is because 3550 only supports Cisco Pre-Standard Power supply whereas 7961G-GE phone only support IEEE 802.3af power supply. Please check the Data Sheet (Power Requirement Section for 7961G-GE Phones)