i have one tight situation.
Already have lan cable in building, but they have only 4 wires (2 pairs)
i need power mikrotik router with at least 5 lan ports over this and data afcros, all with only this 4 wires, how?
If you have 4 cables this is not a network cable
The correct cable have 8 cables (4 pears)
Sorry, this will not be possible.
For 100Mbit passive POE the unused 4 pins of the 8 pins CAT5(5e, 6, 7) cable are used.
For 1000Mbit passive POE the same pins are used but they are modulated over the data signal.
Using 4 pins only is impossible if you wish to transport POE and data. You probably have some sort of ISDN or analog telephone cable, such cable is not usable for network traffic.
Your best solution would be using local power and getting 100Mbit over the 4 pin cable if it turns out to be at least CAT5 cable.
If you indeed have multiple 4 pin cables you COULD use one cable for the 100Mbit data and a second cable to feed the power over the correct 100Mbit POE pins (manually crimping connectors, etc.) and then inject it with passive POE. But this is very sketchy, prone to failure, unsupported and will definitely FAIL if it’s indeed ISDN cable. And most of all, well, euh, you don’t do it that way.
Do it right, or don’t do it! 
4 wires are enough for 100MbitFD. Sure you all already saw/used such cable and it worked pretty good. So the idea to use two cables (one for power only) is not so bad. But anyway rewire with cat6 or better cables for future use is the best you can do.
It is possible to run 100Mbps ethernet + 802.3af PoE over just 2 pairs, using the right kind of PSE (supporting mode A - power on data pairs). Then convert it to passive PoE with MT’s (POE-CON-HP) or UBNT’s (instant 802.3af) converter close to the powered device.
i know that this is not lan cable. this is cable for telephone in first place. But guys who installing make one strange thing.
all apartments have 8 wire inside. But on each floor, in middle, they cut 4 wires from every apartment and join 2 apartments in one lan cable, so in final they need only 1 wire with 4 pairs to get 2 apartment all to the main phone central. now i need to bring signal over this, and power. and for that i can’t rewire
can this router put out 802.3af as i need?
http://www.amazon.com/TP-LINK-TL-SF1008P-100Mbps-8-Port-802-3af/dp/B003CFATT2
Or if who know such device. I found device for end, now just to found device for sending
No, this will not work. I believe this POE standard uses the non-data pins in a CAT5 or CAT5e cable such as suggested here and here.
Your other comment about it starting as an 8 pin cable but that they split later on explains the situation a lot better. The installer put in CAT5 cable but because cable is ‘expensive’ (the installer is a cheapskate and cheater) they split the cable into 2x100Mbit. This works, but is definitely not up to code or supported in any way.
My personal opinion, rip it out and replace it, do it correct. You don’t need to pull a single cable to every apartment/room. You can replace 1 cable, put a small (5 port for instance) switch in a central location and then branch from there. That should save in replacement cost (long cables are more expensive then a little 5p Gigabit switch) and upgrade everything to gigabit while you’re at it! This could also partially give you POE on the cables if you replace the ‘in-the-middle’ switch you are adding with a 5p Gigabit POE model for instance. Or you can passively inject from there.
But again, what you are trying to build right now, please don’t. This is in no way compliant to anything and will cause lots of problems and headaches over time, costing more then the materials and replacing them ever would have. Also, the mess you are now in will be even worse for the next guy again…
just get two gigabit poe-injectors from mikrotik.
then build four adapters to map wires like this:
1->4
2->5
3->7
6->8
this way you can transport 100mbps + passive poe over pairs 4/5 and 7/8
i don’t get what you suggest. if i have 4/5 and 7/8 i won’t start this topic at all
well if power is you priority things left for you is only bridging ethernet over something that don’t need more than one pair.
like AC-ethernet adapters, EoC (http://en.wikipedia.org/wiki/Ethernet_over_copper) or deprecated, but still developed and sold DSL-alike adapters that can use random pair/four wires in any mix at random speed/range(forget tech name. but its quite loud in shDS:L and VDSL -times and usually used over legacy telepone wires or other stuff).
speed would sx then, but it will WORK.
p.s.
add: oh yeah, that thing was HomePNA. second edition was relatively speedy(but more spectrum).
its still used in some buildings over unused anymore cables, like emergency/early warning networks, disconnected landlines and etc.
I’ll try to explain what I would do in that situation..
MT Gigabit PoE adapters work both ways - as injector and as well as splitter.
You can use 2 pairs to transmit power and data, but crimp connector to pins 4,5,7,8.
Recrimp both Gigabit PoE injectors (or build adapters - RJ45 jack ↔ RJ45 connector)
to map wires like this:
1->4
2->5
3->7
6->8
And replace far end GigaBit PoE adapter’s power plug gender (or make adapter)
I haven’t tried this, but it should work..
Hi, you can use may be something from HomePNA. I saw some HomePNA units in student college in Tampere 6 years ago. They used POTS wiring for delivering connectivity to the dorms. There had to be some concentrator in the basement of the building.
Yeah, all these amateur advices…
The ONLY proper way is to put proper cat5 or 6 cable in. If price of the cable is the issue, well how serious are you in your work anyway?
I mean, for less than 100usd you have 305meter of cat5e cable with connecters and a proper crimper tool… If that is too expensive and you’d rather start ‘playing’ with all kinds of ‘fixes’ go to some other hobby forum to talk about these…
@econet
Use Ethernet over VDSL2 Converter (http://www.planet.com.tw/en/product/product.php?id=21749).
Only one cable pair is necessery for data transmission, so second cable pair is available for power.
HTH,
thats a correct answer, but judging from his input - seems he dind had authority/right to do so.
you had point here, sure, proper cabling saved him from lot of headache but folks tend to be be bound to subordination/heararchy and aside you rude bravado sometimes even such decisions isn’t up to common networking grunts.
just a guess. he may be really lazy as you suggested/implied, but more frequently i was saw terrified cablings in office buildings was cause anyone horrified idea to step up and ask for permission(nor there already cazualties of such attempts).
people had to deal with lot of Legacy stuff in Real world, sadly without SLightest chances to break and re-build something properly, sometimes. even self-employed and small companies do, sometimes.
and lot of Formal regulations/restrictions, suggestions, that sometimes had fuzzy legal status, but enforced heavily even at municipal level 
im not lazzy, i have km and km of lan cable, is not problem in this.
in one building i have about 5 clients to connect. but problem is that i don’t have permission to put wires where somebody can see them. i can use only instalation that is built in. i can even replace it, but when they make building, one part of space for cables colapse, and now you can’t remove existing cable to put in new one.
only solution for “building representative” is “They can use service from some other providers, they will get they internet”.
but why not try something that can work… and we can make some money…
Working, only 2 pairs, data +12 V power. When i get time i will draw schema.
TNX to sup5 for idea.
Hi, please let us know how and with what type of equipment you managed to solve this.
Appreciate!
Sorry for the raising this from the dead.
I have an issue where I’ve lost a pair of cables according to my cable tester. It was running to 1 of 2 cameras with a complete second cable running to the same place for the other camera still working fine on all 4 pairs.
I got a POE combiner the type that uses 1,2,3 & 6 and 4,5,7 & 8 separately which works with a generic 802.3af/at switch, but not with the Mikrotik. I’ve tried forcing the POE high power on and negotiating to 100M baseT, but I don’t get a link or any draw on the POE.
Does anyone have any ideas that I can try to get these cameras both working either using the splitter using the remaining 3 pairs of the original cable?