I have a Cisco WS-C2960X-24PSQ-L switch. This is a IEEE 802.3at PoE+ switch. Connected to it is a Yealink SIP-T48G phone (IEEE 802.3af class 0). I needed to add a device near the phone so I bought a GS105PE (V1.6.0.6). I connect the Cisco to port 5 (PoE PD port). I get 2 lights, amber solid and green that flickers with traffic. If I plug the Yealink into port 1 or 2 (PoE PSE ports) I get flickering on the port's green LED that matches the PoE PD port green LED flickering. However the phone does not power up.
I tried the same using a Cisco WS-C3850-24P switch with the same results (also IEEE 802.3at PoE+)
Should this work or is there and issue with running 802.3af devices when powered from a 802.3at switch?
Should basically work, assuming no limits configured on the ports (and of course assuming that both tested switch models have not hit the max total PoE). What shows:
On the 2960 the Yealink is the only PoE device. It is rated at 2.4-10.5W. The 2960 is rated 30W (IEEE 802.3at) so unless the GS105PE pushes 20W power shouldn't be an issue. I've also tried to get the GFS105PE to power a Digi Portserver TS 2 P MEI (IEEE 802.3af, rated 4-6W) and had the same result.
some additional info - The LED on the PD port indicates the GS105PE thinks the Cisco is a 802.3af switch and not a PoE+ switch. This occurs on both the Cisco WS-C2960X-24PSQ-L and the Cisco WS-C3850-24P switches. I have a Engenius EWS 7928P switch. The GS105PE thinks it is a 802.3af switch also (it is PoE+). I found a junk Adtran 1531P switch and finally the GS105PE recognized it as a PoE+. As best I canm tell, the GS105PE seems to have problems recognizing PoE+ switches properly.
On the 2960 the Yealink is the only PoE device. It is rated at 2.4-10.5W.
That's most lilkey not relevant, because it does request (and reserve) a Class 0 device - 802.1af units do this based on a pulsing negotiation. If the GS105PE PD does not get (or recognize) the 802.1af, it is not able to power-up the Class 0 device - because there is not enough power available.
The 2960 is rated 30W (IEEE 802.3at) so unless the GS105PE pushes 20W power shouldn't be an issue. I've also tried to get the GFS105PE to power a Digi Portserver TS 2 P MEI (IEEE 802.3af, rated 4-6W) and had the same result.
This requires that both ends of the link agree - otherwise there won't be power. Unfortunately there is more than a simple Watt math involved in PoE.... That's not "rated" - it will be able to provide power as per the 802.3at standard, based on the pulse based negotiation and/or LLDP. If it does not (that's why I have asked for the PoE port information of your Cisco device above...).
Funnily, there are two technologies creating misunderstandings in networking for years - one if FTP over NAT, the other is PoE...
The LED on the PD port indicates the GS105PE thinks the Cisco is a 802.3af switch and not a PoE+ switch. This occurs on both the Cisco WS-C2960X-24PSQ-L and the Cisco WS-C3850-24P switches.
That's why it can't and won't power the 802.3af Class 0 device ...
I have a Engenius EWS 7928P switch. The GS105PE thinks it is a 802.3af switch also (it is PoE+). I found a junk Adtran 1531P switch and finally the GS105PE recognized it as a PoE+. As best I canm tell, the GS105PE seems to have problems recognizing PoE+ switches properly.
There are always two ends in the PoE, PoE+ and higher standards. Both ends can be wrong, or cause issues.
