UniFi Lab 02
PoE budget blowout
APs and cameras keep dropping. The Flex PoE warning is trying to tell you something.
Your job: keep both APs and the camera Connected at night, with IR on, and clear the PoE warning.
This run: Break AF. USW-Flex on U-POE-AF, two APs and a camera, night.
Lab complete. The Flex is inside its PoE budget at night and every device stays Connected.
poe_ok_stableConnected, within PoE budgetTopology
Site: PoE lab, night- Gateway optionalData only in this lab. Feeds the injector LAN jack.Online
- LAN: data only, no PoEGateway to injector LAN jack.
- Injector Power runs short hereU-POE-AF
Class 802.3afInput ~15.4W inFlex budget about 8W
injector_undersizedInjector too small for this load - Port 1, PoE in: 802.3af, about 8W downstream38.0W max needed. The link is up, the watts are not there.
- USW-Flex5 port switch, powered on Port 1, PoE out on 2 to 51in25.4W30.0W40.0W5
Max draw, what UniFi budgets38.0W of 8W, 30.0W over
Live draw, what you see now18.7W of 8W, 10.7W over
poe_budget_exceededExceeded total PoE budget - Ports 2, 3, 4: PoE outThe Flex cuts a port when the camera asks for its night watts.
- AP LobbyU7 class access point, Port 2ConnectedAt risk on the next reboot
Live 5.4WMax 13.0W
- AP OfficeU6 class access point, Port 3OfflineDropped when the camera rebooted
Live 0.0WMax 13.0W
device_disconnectedOffline - Camera, Front doorG5 Bullet class Protect camera, Port 4OfflinePort cut, reboot loop
Live 0.0WMax 12.0W
IR on, nightdevice_disconnectedOffline
Legend
- Power and data, inside budget
- Power runs short on this link
- Data only, no PoE
- Connected or allowed
- Offline or over budget
- Warning, not a win
PoE insights
USW-Flex, ports 2 to 5Input: Port 1 from U-POE-AF, 802.3af. Downstream budget about 8W.
| Port | Device | Mode | Live | Max |
|---|---|---|---|---|
| 2 | AP LobbyConnected | Auto | 5.4W | 13.0W |
| 3 | AP OfficeOffline | Auto | 0.0W | 13.0W |
| 4 | CameraOffline, IR on | Auto | 0.0W | 12.0W |
| 5 | Empty | Auto | 0.0W | 0.0W |
| Total | 18.7W | 38.0W | ||
| Downstream budget | 8W | |||
| Headroom at max | 30.0W over | |||
Live is what the device draws right now. Max is the documented maximum UniFi budgets for, camera IR on. Watt values are example numbers for teaching.
Controls
The settings you can change in this lab. Everything else is fixed.
Flex power input, Port 1
The injector that feeds the USW-Flex. This sets the downstream budget.
Per-port PoE mode
USW-Flex PoE out ports. Mode sets what a port may offer, not how many watts the Flex has.
Camera, Front door
On shows night draw. The budget uses the camera max either way.
Out of scope for this lab
Why this fails
copy key: injector_undersizedAF injector on a loaded Flex
USW-Flex has exceeded total PoE budget of 8W. This can cause device disconnects. Please offload devices to new switch or PoE Injector.
Field note: Daytime draw looks fine. UniFi budgets the max each PD can take. An AF injector starves the Flex. Here that is 38.0W max against about 8W out.
Fix: Swap to PoE++ / POE-50-60W. Offloading only the camera still leaves two APs, about 26W, over an 8W or 20W Flex budget.
Cameras jump watts when IR turns on
AP Office: Offline. Camera, Front door: Offline
Field note: Cameras jump watts when IR turns on. Budget for night, not noon. When the Flex runs short a port drops, the device reboots, and the boot draw can knock the next one off.
Fix: Fix the budget. Turning IR off is not a fix.
Why Broken and Fixed
Console words
- has exceeded total PoE budgetShowing: 38.0W max of 8W
- This can cause device disconnectsHappening now
- OfflineShowing: AP Office, Camera
- Connected1 of 3, at risk on reboot
Glossary
Core, Labs 01 to 03- Native
- Untagged VLAN on a switch port (PVID). Management traffic usually rides here on UniFi device uplinks.
- Tagged
- VLAN IDs carried with an 802.1Q tag on a trunk. Guest and IoT SSIDs need their VLANs tagged on the AP uplink.
- Access port
- One VLAN only, untagged. Fine for a printer. Wrong for an AP that serves multiple SSIDs.
- Trunk
- Native + tagged VLANs. Correct pattern for UniFi switch to AP / switch to gateway when multiple networks exist.
- ZBF
- Zone-Based Firewall. Policies between zones (Gateway, External, Internal, Guest, etc.), not just classic LAN IN rules.
- Gateway zone
- Where the router answers DHCP and DNS for a network. Block Guest to Gateway and clients get No IP or DNS unreachable.
- Client isolation
- WiFi setting that stops guest clients from talking to each other. Keep on for Guest.
- PoE class
- AF (~15 W), AT (~30 W), BT / PoE++ (higher). UniFi budgets on documented max draw, not quiet daytime watts.
- PoE budget
- Sum of max PD draws vs what the switch or injector can supply. Exceed it and devices disconnect.
- Injector
- Power source for a Flex or similar. Wrong class (AF on a loaded Flex) is a classic field fail.
- Max draw
- Datasheet maximum watts for a PD (IR on, boot). UniFi PoE budget math uses this, not the quiet live reading.
- Flex budget
- USW-Flex downstream totals by input: AF 8W, AT 20W, BT or 60W injector 46W (set Power Source to PoE Injector).
- Remote Unlock via Endpoint
- Access setting. When off, Endpoint receivers can talk on a call but cannot unlock.
- Door Attendant / receiver
- User assigned to get the door call. Not on the list means no Unlock for that door.
- Inform
- Device check-in URL to the Network application, usually controller host on port 8080, path /inform.
- STUN
- UDP 3478 helper for L3 / remote adoption. GUI on 443 is not the same path.
Fiber terms, glossary ready for later
MM and SM grades, cage form factors, DAC, AOC, and complementary BiDi ends. Full rows land with the fiber-sfp-dac lab.
Symptom words (overlay language)
Before and after
Diff rows marked| Setting or symptom | Broken start | Now |
|---|
Gear in this lab
- 1 Gateway (optional)
- 1 Injector, U-POE-AF
- 1 USW-Flex
- 2 Access points
- 1 Protect camera
This fix needs different hardware, not a setting. Counts only, no prices.
Takeaway
Budget for night, not noon
Daytime watts look fine on a Flex until the camera turns IR on or everything reboots at once. UniFi budgets the documented max of every powered device, so size the Flex input for that number.
- Add up the max draw of every AP and camera, IR on.
- Match the Flex input to it. Two APs and a camera need PoE++ / POE-50-60W, not an AF injector.
- Plan around about 46W out from a 60W injector. That is the switch, not a broken adapter.
- Still tight? Move the camera to another PoE switch. On this lab, that alone does not clear an AT budget.
BOM delta on win
| Item | Broken start | After fix | Change |
|---|---|---|---|
| Injector, U-POE-AF (802.3af) | 1 | 0 | Remove 1 |
| Injector, U-POE++ / POE-50-60W | 0 | 1 | Add 1 |
| USW-Flex | 1 | 1 | No change |
| Access points | 2 | 2 | No change |
| Protect camera | 1 | 1 | No change |
Offloading the camera onto an AT injector still fails here. Two APs are 26.0W max against a 20W Flex budget. PoE++ / POE-50-60W, about 46W out, is the clean fix. Counts only, no prices.
Want APs and cameras powered like this at your place? We size PoE budgets and install Protect cameras as part of a UniFi install.
A teaching lab, not a quote and not a design for your site. Watt values are simplified examples from the UniFi Network app PoE view. No account, and nothing from this lab is saved.