TravelingPacket – A blog of network musings

Currently I am working with a client who has lots of Ruckus ICX 7250 PoE+ switches. These have been great switches, lots of features such as: large PoE budget, 10G, VRF/Routing capability. Recently the client has rolled out Mitel headsets that charge from their larger handset phone stations.

Strange issue has been happening though, when they put the headset in to charge the phone reboots, and the switch throws an error (you will see below) and basically kills power to the port, thus everything reboots. After some quick analysis it seems like the phone station is requesting 802.11AF (15.4 watts max) and then when the headset gets turned on to charge it spikes above 15.4 watts for a bit, and making the switch rightly throw the error. The phone pulls somewhere around 1-3 Watts, and the headset seems to add an additional 3 (according to its documentation). Still well within range of 802.11AF.

Link to Mitel headset: https://www.mitel.com/en-us/products/devices-accessories/ip-phones-peripherals/other/integrated-dect-headset

This is an assumption, I might go through and do some debugging and see if that’s the exact issue, but adding some commands to the switch did fix the problem. So before we go through commands and analysis; the commands used to resolve the issue basically set each port to 802.11AT which allocates 30 Watts for the port. An issue with this: simple math indicates that if we have a 48 port switch with a 740 Watt PoE budget, we can only really give each port 15 watts if every port is powered up. That’s true, but luckily we aren’t going to run into that problem here. Few headsets/Power needing ports.

When the headsets were plugged in the switch started throwing these errors:

Dec 20 19:41:27:C:System: PoE: Power disabled on port 1/1/19 because of PD overload.
Dec 20 19:41:27:C:System: PoE: Power disabled on port 1/1/19 because of PD overload.

This would then disable PoE on the port for a few seconds and make the phone reboot.

When checking to see how much power the phone was pulling the following was done prior to the fix commands – Please just look at Port 19:

The phone was showing up just asking for 3.6 Watts and it was only allocating 15.4.

Lots  of ways to tackle the fix to this problem, the approach I used is to modify the allocated power by class – So instead of letting the switch decide how much power to allocate by letting the device tell it – I am forcing the switch to change the power class for the phones (in this case 3 ) to 4. This allocates a default of 30 Watts. Below is Ruckus’s outline for the Power classes

The commands to modify this:

interface ethernet 1/1/19
inline power power-by-class 4

After applying these commands check Port 19 out:

All devices are still requesting pretty much the same amount of power they were before except now we see the headsets requesting power as well. Not only that but each port does have 30 Watts allocated to it. So the thought that we could run out of allocated power if we had a lot of phones/PoE devices plugged in is a real concern. Right now, even though we are only using 47.7 Watts, the switch has provisioned 390.

There are better commands to use other than the power-by-class that I used. For example, since we know the phone with charging the headset only needs little over 4 Watts we could use the command “inline power power-limit 25000” to allocate 25 Watts instead of the full 30. This number could keep being modified to find the exact number where the port drops. Or you could just modify the ports with headsets only – But, like I mentioned above we have no real need to do that, so the power-by-class blanket command works fine in this case.

After applying the above command check out port 19’s PoE allocation:

Lots of ways to fix this issue, but all modify the amount of power allocated to the port.