Perpetual and Fast POE implementation

Charlie Jones · ‎10-04-2023

I am going to be upgrading the IOS on my 9300 switches due to a bug with IOS 17.6.5 and DNAC. I would like to enable Perpetual and Fast POE on my 9300's now. My question is will those features be enabled after the switch upgrade? The documentation for this feature only mentions that this should be configured before connecting devices, or performing a shut/no shut on the interfaces. I was hoping to hear that a switch reboot would work.

Reza Sharifi · ‎10-04-2023

Have never tested this but if you are planning on enabling it on all ports, a reboot should do the same as it will draw power from the ports before reloading the switch.

HTH

Leo Laohoo · ‎10-04-2023

We have Perpetual (and Fast) PoE enabled on all our switchports.

Before rebooting the switch, enable the two commands:

 power inline port perpetual-poe-ha
 power inline port poe-ha

Disable the ports for about 5 seconds and then enable the ports.

Wait for the PD to boot up before rebooting the switch.

What we have seen with Perpetual PoE is when we issue the command "reload", the PD do not power down. APs and VoIP remain powered up when the switch goes into a warm reboot. For obvious reasons, during the warm reboot of the switch, network connectivity is lost and the PD are just "flapping in the wind". When the switch boots up, the PD re-connects to the network not soon after.

Charlie Jones · ‎10-05-2023

Thanks Leo.

I had an understanding of what needed to be applied to the switch ports. The part I wasn't sure is if the switch reload after an upgrade would reset the PD. I'll follow what you described as treat the IOS upgrade and the enablement of Perpetual/Fast POE as two separate change events.

Leo Laohoo · ‎10-05-2023

@Charlie Jones wrote:
The part I wasn't sure is if the switch reload after an upgrade would reset the PD.

Yes and no. It will depend on the sequence of events.

Perpetual PoE does not kick in just by entering the commands. There is a reason why I said manually disable the port, and subsequent waiting for a few seconds, before enabling the same port.

The system needs to first "know" how much is the power draw. And the system would not have any idea without the ports bouncing (disable/enable the ports after a few seconds). After doing this, warm-reboot (as opposed to cold-reboot) and the PD will still have power while the switch reloads.