Hi all and thanks for the coming answers.
I have 3 power connect 5548 working just fine. Suddenly 5 ip phones just stopped working. They're not able to connect anymore. I made no changes, no modification so I don't understand why it stopped working. The LAN is just fine.
In the LLDP neighbors information, I have 35 devices, mostly ip phones and only 5 phones not working on the same switch the number 2.
The only difference I see is on the "LLDP MED Capabilities"
I see that on a phone connected "Capabilities, Network Policy, PoE-PD, Inventory"
and that on a phone not connected "LLDP MED Capabilities Capabilities, Network Policy"
Phones are ok because if I switch them to a working phone everything is ok again, so the problem is related to the dell switch.
Maybe you can help, I can't offer myself to reboot it...
I have no green ethernet option enabled.