Ubiquiti & PoE Story

[khat17]

So. Have a small networking story to share with some equipment at home. Just FYI in case you attempt something similar.

So my setup involves an ER-X and a PoE Unifi AP. I had the setup with passthrough PoE to the AP so that I'd use one power adapter for both devices. Everything was up and working fine, however I realized I had periodic slow speeds. No idea why. When the speeds dropped I would check all kinds of things and started blaming FLOW.

Ping to the ER-X would be fine but I'd have dropped packets to the modem. Direct connections to the modem would give full speeds but through my AP it would be greatly reduced and fluctuating. No idea why because the Ubiquiti should give me better quality connectivity (and control) overall.

After changing out some of the cables to CAT6 - this after I replugged cables and things worked from the slow speeds - the speeds dropped again and I couldn't figure why. I decided to try one last thing.

I used a power adapter for the ER-X and the PoE injector for the AP only instead of using the passthrough. So far it's been 2 days and no problems so far. Speed tests have been consistently good with or without other devices using internet.

If this works for the rest of the week with no other speed drops - it will be a lesson in overall power/usage by the devices. I had thought that the small power draw from the ER-X should not degrade the service from the AP - but it may not work like that at all.

So in summary - if you have PoE equipment that offers passthrough. Unless you're SURE that the provided power from the PoE will be able to supply both devices - use direct power. There's also the fact that the ER-X carries a fuse internally and limits the overall power going through - so the AP may need more for certain operations and it may be bottlenecked by being shared through the ER-X.

The solution would have been to use a PoE switch, but I didn't have one available and was just testing. But hopefully you won't make the same mistake or if you're considering something similar you'll know what to expect.

[Falcon1986]

I know this thread is a few months old, but I thought I should mention something here for anyone else considering a similar setup.

When using PoE hardware, pay attention to the PoE standard supported at the PoE switch and the PoE-powered AP that you intend to use. I have this same router, but I chose to use a US-8-60W as my PoE switch to supply a UAP-AC-Pro and a UAP-AC-LR. If you look at the UAP-AC-Pro’s data sheet, it explicitly states that it requires 48V passive PoE (802.3af/bt) with a maximum power consumption of 9W, while the UAP-AC-LR will be satisfied with 24V passive PoE (802.3af/A) with a 6.5W maximum power consumption.

The ER-X wouldn’t be able to supply the Pro, but it could probably be sufficient for the LR. That being said, even Ubiquiti admits that a more powerful input source might be required (see page 4 of the documentation) over the power adapter that comes with the ER-X, as the EdgeRouter can consume up to 5W by itself.

So, sticking with the PoE injector that came with the AP is the safest option and less likely to require spending more money. But if you do decide to not use the PoE injector, you’ll need to upgrade the power adapter of the ER-X, provide the ER-X with PoE-in power or use a dedicated PoE switch with an adequate power budget and supported standards for the AP(s) you wish to use.

[khat17]

Agreed and correct. Some users have also used higher output adapters with the ER-X to compensate for the added power draw. I wasn't going to do this as there is the potential to fry the ER-X if the output is too high.

I know this thread is a few months old, but I thought I should mention something here for anyone else considering a similar setup.

When using PoE hardware, pay attention to the PoE standard supported at the PoE switch and the PoE-powered AP that you intend to use. I have this same router, but I chose to use a US-8-60W as my PoE switch to supply a UAP-AC-Pro and a UAP-AC-LR. If you look at the UAP-AC-Pro’s data sheet, it explicitly states that it requires 48V passive PoE (802.3af/bt) with a maximum power consumption of 9W, while the UAP-AC-LR will be satisfied with 24V passive PoE (802.3af/A) with a 6.5W maximum power consumption.

The ER-X wouldn’t be able to supply the Pro, but it could probably be sufficient for the LR. That being said, even Ubiquiti admits that a more powerful input source might be required (see page 4 of the documentation) over the power adapter that comes with the ER-X, as the EdgeRouter can consume up to 5W by itself.

So, sticking with the PoE injector that came with the AP is the safest option and less likely to require spending more money. But if you do decide to not use the PoE injector, you’ll need to upgrade the power adapter of the ER-X, provide the ER-X with PoE-in power or use a dedicated PoE switch with an adequate power budget and supported standards for the AP(s) you wish to use.