I recently had an issue when deploying some new Cisco 9176 Meraki cloud managed access points. The access points connect to Cisco Catalyst 9300 switches. Deployment went as expected without any hiccups. That is until the site experienced a power outage. During the outage the switches rebooted and of course, the access points did as well. Upon power on the access points were running in low-power mode. The 6GHz radio was disabled and both 5GHz radios were reporting -1dBM and not allowing client connections. See images. There is no 2.4GHz radio as the flex-radio is being used for a 2nd 5GHz radio. Power to the access points was cycled via the switch and they resumed normal operation.
Initially this was written off as an anomaly. The switches are not provided power via UPS and power outages being unpredictable, we believed this to be caused by dirty power to the switch during the outage.
About a week later, the problem occurred again. The access points were cycled once again via the switch to restore connectivity.
A lab environment was created, and the problem was noted as reproducible during a cold reset of the switch but not when issuing a reload command.
The interface configuration included ‘power inline port 2x-mode’, power inline port perpetual-poe-ha’, and ‘power inline port poe-ha’. ‘perpetual-poe-ha’ and ‘poe-ha’ were removed and the switch cold reset. Without perpetual-poe enabled, the access points boot and work as expected at full-power and full-capabilities.
A call was placed to the TAC thinking this was a bug, and after multiple test iterations, it was determined that UPOE+ needed to be enabled via the ‘hw-module {switch_no} upoe-plus’ when perpetual-poe is enabled for the access point to negotiate power properly during a cold reset of the switch.
This seems counterintuitive as the access point can draw no more than 39W and functions properly when powered on separately from the switch. Perpetual poe documentation also does not mention the need to enable UPOE+.
This behavior was not tested with other models, but I expect it is the same on other Cisco UPOE+ switches.
If you’re deploying 9176s and need to use perpetual poe, do yourself a favor and enable UPOE+. Otherwise, leave perpetual poe disabled. I’ve included links to the 9176 data sheet and the perpetual poe guide.