So if natively enabled how it is decided to use POE or POE+ ?
Is it based on the end device which connects to the switch port & how much power it requires ?
Is it totally depending on the end device power requirement ?
My device does not support both CDP & LLDP. Let me know what is the command to manually configure how much power to "feed" to the end device.
Try this command under the interface that is connected to the device and assign power to a statically.
power inline static max xxxx
The device which I am going to connect has the attached specification.
So what should i do for this to work.
There will be around 20 such devices which will be connected to 48 port switch.
So my understanding is that i need to manually confgure the below command in each of the 20 switch port.
power inline static max 19000
Let me know if my understanding is right.
CDP & LLDP only happen AFTER the device has powered up. PoE/PoE+ uses a more 'basic' mechanism that has to kick in first. You don't need to manually configure the power on any of the interfaces assuming you aren't planning to oversubscribe the PoE on the switch. Once the PD device has booted then CDP/LLDP can do additional things that aren't possible with the 802.3af/at standard.
Read this https://en.wikipedia.org/wiki/Power_over_Ethernet and the other post with a link to the 3750 PoE troubleshooting.
so for devices which does not support CDP/LLDP , i have to manually set the required power on the interfaces if the requirement is more than 15.4W
No, you do not need to manually set the power. The 802.3af/at mechanism will negotiate the Class of the attached PD device. LLDP is optional and allows for more granular power requirements. The five classes (0 - 4) allow for 15.4W, 4W, 7W, 15.4W and 30W respectively (Class 0 is for a device that doesn't support 802.3af/at Class negotiation). Once a device has booted CDP/LLDP can signal more granular requirements.
If your devices don't signal their PD class - i.e. they are Class 0 - then they will be allocated 15.4W. Any 802.3at PD Class 4 device should be detected as a Class 4 device. If it doesn't then it isn't complying with the standard and I'd be reluctant to plug it in...
A device that is detected as Class 4 will initially be allocated 15.4W only. Once its booted and CDP or LLDP kick in it can request more power up to 30W. If your Class 4 device doesn't support CDP or LLDP then it will only be allocated 15.4W. I am guessing a prerequisite for 802.3at is LLDP support on the PD (or at least that is what the Catalyst is expecting). Are you sure your device doesn't support LLDP? Have you enabled LLDP on the switch as it isn't on by default.
Some notes here that are similar I think - https://community.ui.com/questions/Workaround-for-UAP-AC-802-3at-non-compliance-POE-power-problems-reboots-for-newer-Cisco-catalyst-/baf59f23-e89c-4042-8349-d05b6e3e95b7