PoE does not work over self-built CAT5E cable

[the-ninth]

Hi,

In my house I have just installed a new CAT5E cable (F/UTP) and crimped my own RJ45 connectors (CAT6 STP) on it. Gigabit network connectivity works fine, but for some reason PoE does not. I am trying to power an Unifi Flex Mini switch from an Unifi Lite 8 PoE switch. When I connect the two devices via a bought CAT5 cable it works, only via the cable I installed myself it does not.

What could be the cause of this? Is there anything that could be wrong in the way I crimp the connectors that would leave Gigabit connectivity working but not PoE? Could it be related to the connectors being CAT6 STP and the cable being CAT5 F/UTP?

Any advice/insights would be highly appreciated!

Regards, Robert

 

[bbunge]

Did you do the ends to TIA/EIA 568b?
Even if you crimped the ends correctly you could still have a bad connector.

 

[the-ninth]

Yes, the cable has 568B printed on it, and I did the ends according to T-568B.

What do you mean exactly by "bad connector"? To be honest, I do not know really how PoE works, what could be wrong with the connector that would make PoE not work while Gigabit network connectivity works?

 

[bbunge]

Yes, the cable has 568B printed on it, and I did the ends according to T-568B.

What do you mean exactly by "bad connector"? To be honest, I do not know really how PoE works, what could be wrong with the connector that would make PoE not work while Gigabit network connectivity works?

Well, the important part is the Cat5e. It is the ends that need to be connected per 568B. If you are using solid wire cable it can sometimes be a problem to get the ends crimped right. Test the cable and it works. Plug it into a device and it doesn't. better way is to use a punch down female connector and a patch cable to the device. I use these: https://www.amazon.com/gp/product/B005E2Y9WY/?tag=snbforums-20

With your mini PoE switch it is apparent which port the PoE cable gets plugged into so it is not operator error..
A cable continuity tester also comes in handy with Ethernet cabling to make sure the wires are in the correct place.

 

[the-ninth]

Thanks! The cable I installed is a patch cable, not solid wire. So it should work well with the crimped connectors. But anyway, I ordered a tester to check this further, and along with it some connectors similar to the ones you linked. Will report back on the results.

 

[the-ninth]

One more thing. So I read up a bit now on Gigabit Ethernet and PoE. From what I understand, Gigabit Ethernet uses all eight wires of the CAT5E cable. So if Gigabit Ethernet is working, all wires seem to be connected correctly. Now I am wondering again, why would PoE then not work? Could it be that one of the wires is only partially connected, well enough for the data transfer, but not well enough for PoE? Sorry if that is a dumb question, but I am a software guy and not well-versed on the physical side of the business.

 

[the-ninth]

OK, found the issue and have to admit it was an operator error after all. I did not realize that only four of the eight ports of the Unifi Lite 8 PoE switch have PoE. When testing with a normal patch cable I used a different port than when testing with my self-installed cable, which is the reason why one worked and the other did not.

Still, I do not yet trust my own cable completely. When connecting it initially to a PoE port, I got PoE but only 100MB connectivity. I then changed the port configuration manually to 1GB, which worked. After that I changed the port back to auto-negotiating the speed and it remained at 1GB. Not sure what lead to the 100MB initially, maybe the wires are really not connected perfectly, leading to such unpredictable behavior.