What happens when your POE devices require more budget than is offered?

[thecomputerguy]

Replacing a Gateway, Switch and AP's at a church.

Very low maintenance, not a lot of users simultaneously but they do have 4 AP's in the building.

They are currently using a D-Link 16-Port 10/100 switch, an old Unifi 8Port Poe Switch, which powers 4x UAP-AC-HD's.

I am replacing their Gateway with a UDM-SE, also bought a 24Port POE Switch, to power 4x U6 Enterprise AP's.

I figured I'd just buy the best AP's Ubiquiti offers and be done with it. Now that I have the equipment I am discovering that I made some mistakes.

1.) The U6 Enterprise AP's can operate their LAN connection at 2.5GB.
- I'm not too worried about this. Obviously it looks like I over spent on these since 2.5GB is built into the cost but I don't think this customer would know the difference anyways since they currently run on 10/100 so 100/1000 is a huge upgrade.

2.) The U6 Enterprise AP's have a max power consumption of 22W

- The UDM-SE (172W??) has 2x POE+ and 6x POE but also says


- The 24P POE Switch (95W??) has 16x POE+ but also says


When I plug all 4x U6 Enterprise AP's into the UDM-SE on the POE side (NOT POE+) they all light up, adopt, get configured and everything "looks like it's fine" at idle they are consuming about 12.25W.

I have 4 AP's but the UDM-SE only has 2x POE+ and 6x POE.

Obviously I'm going to plug them into the 24P POE+ Switch so I wont be hit by POE budget. But theoretically, what would happen? Just poor performance, or would the AP power cycle? What are the chances of the AP even getting near a 22W budget when were probably looking at 20-30 users?

I know for sure I overbought on the AP's but I'm not about to return them just because I can't utilize 2.5G.

 

[nlinecomputers]

Not sure. It depends on how sophisticated the power control circuit is in that switch. If well designed it will just cut off after it applies the proper power to the first devices in line about 4? Number 5 probably will not get power. If it doesn't have good power management it will starve out and you'll have 5 flaky units. The units will tend to draw more power if there are lots of conflicting signals nearby. They try to be "louder" and thus draw more power. Lots of endpoint connections and data traffic will also bump up the power use on these units.

 

[YeOldeStonecat]

It will randomly cut power on random ports once the POE budget is hit.
On the LCD screen of your UDMP, navigate to find the POE budget section.
APs fluctuate on their "thirst"....due to amount of clients, amount of traffic passing, etc. So just sitting there idle...likely never peg the budget. But get busy in the day...they'll get thirsty.

Choose your POE switches based on assuming max power consumption of devices.

Recommend always starting with the USW "Pro"" switches too...those entry level USW's have too many shortcomings. Go Pro, or for bigger jobs...the enterprise models.

 

[NETWizz]

To answer the questions, it depends. Most PoE+ devices don't take the full 30 watts, but if they need more than 15.4 W they can become unstable and reboot or lockup. I have seen other devices signal they don't have enough power and request PoE be stopped.

There is a log entry and PoE goes offline in that case.

The current stuff I am buying at work has UPOE, which is better than PoE+. Most devices just ask for PoE and even then are mostly class 1 or class 2 devices