How to enable POE?

Installing and Using OpenWrt
1

Just finished installing OpenWRT, having trouble understaing how to configure POE. I already have POE working on ETH0, but ETH4 is not working. I googled and found instructions, but having trouble understanding. The following set the corresponding value variable in /etc/config/system: - where exactly is that in the GUI, or does it have to be done on some command prompt?

Also, it says Update: Snapshots with Kernel 5.4 may use a different GPIO number for PoE passthrough. Try 480 instead. I'm on kernel 5.10.176, would that apply to me? Thanks

The router can supply PoE out (passthrough) on the eth4 port. This is controlled with GPIO 0.

Note: Supported Voltage Range is 9 to 26VDC. The original power supply has 12VDC. For e.g. a 24VDC passive PoE a new 24VDC power supply is needed.

To enable PoE out (passthrough) set the corresponding value variable in /etc/config/system:

config gpio_switch 'poe_passthrough'
        option name 'PoE Passthrough'
        option gpio_pin '0'
        option value '1'
A reboot is require to activate the change.

!!! Update: Snapshots with Kernel 5.4 may use a different GPIO number for PoE passthrough. Try 480 instead:

config gpio_switch 'poe_passthrough'
        option name 'PoE Passthrough'
        option gpio_pin '480'
        option value '1'
2

Is this for an ER-X? (The model is not mentioned anywhere in your post)?
What are you trying to power using the poe pass though? And what is your power supply?

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3

Yes, sorry, it's an ERX. I have ETH0 POE and want to do passthrough to ETH4, which is an access point. The power supply is 24V, 0.5A.

4

What access point, specifically?

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5

UAP-AC-LR
https://dl.ubnt.com/qsg/UAP-AC-LR/UAP-AC-LR_EN.html

6

So I wouldn’t recommend powering the AC-LR via the pass-though. This can result in a brownout condition in the er-x under certain circumstances (the max power consumption of the ap is 6.5w and the er-x is 5w. While that is technically within the power budget afforded by that supply, it doesn’t have much headroom and the router may have trouble when you are doing high bandwidth transfers. There are several threads about this in the ui forums (the solution is simply to power them individually).

I cannot answer your question, though, about how to actually enable the pass through.

3 Likes
7

Thanks for the warning. I'll skip POE in this case.

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8

The PoE output on port 4 has no protection against overloads etc. Only devices compatible with 24 volt passive POE must be connected when the PoE out is enabled. Connecting a non-POE device or an IEEE af/at device is very likely to result in hardware damage.

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9

In the case of the UAP-AC-Lite and LR models, they are 24V passive PoE compatible. But for all readers of this thread, @mk24 's warning is very important to consider -- many devices that are not designed for PoE may be fried if passive PoE (i.e. always on, no auto-detection) is applied.

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