LAN with CAT3 (telephone) wiring?

[nbarb99]

This question is more from a curiosity standpoint (the network geek in me ) than an actual implementation standpoint ...

Is it possible, and how, to run a LAN (10Mbps) over CAT3 standard telephone cabling (two-pair I assume)? I've seen a few mentions of things like this, i.e. 10baseT4, 100baseVG, PhoneLine, etc.

I'm interested in any links, articles, etc... I love geeky info

 

[ScottMac]

Cat3 is the normal spec for 10Base-T.

If you meant 100 meg, then 100Base-T4 and VG used all four pair, ~25 meg per pair.


FWIW

Scott

 

[cmetz]

nbarb99, if all you need is 10Mb/s over cat3, just take your favorite 10/100 gear and manually configure the speed to 10Mb/s. You MUST manually configure the speed - otherwise most gear will try to sync at 100Mb/s, and they'll probably do so, they just won't be able to maintain a reliable link and you'll have a lot of headache.

There was a 100BaseT4 spec to do 100Mb/s over four pairs of cat3, but it was short lived. I'd be surprised if you can find any current gear supporting it, though you might be able to find some stuff on EBay. Hope you have ISA or EISA slots, too

 

[rw120555]

Would Cat3 work better or worse than just getting homepna equipment?

 

[cmetz]

Better.

 

[martind1]

cat3 will work fine for 10bt networking.

you shoudlnt need to manually configure the gear to handle 10bt, most newere HW is autodetect.

 

[nbarb99]

So, *theoretically*, you could crimp RJ-45 ends onto a CAT3 cable and it'd work?

 

[ScottMac]

There's no theoretically about it. Cat3 is the spec for 10 meg / 10BASE-T, as are RJ45 connectors.

Not all UTP is rated though, there is such a thing as "plain old phone cable" which is NOT Category spec, and may work, but will suffer performance-wise.


If the cable is Category rated, it'll say so on the jacketing of the cable. If it doesn't say Category Rated Cat(3,4,5,5e,6), it's unrated cable.

Good Luck

Scott

 

[martind1]

Originally posted by: nbarb99
So, *theoretically*, you could crimp RJ-45 ends onto a CAT3 cable and it'd work?

as long as you crimp the wires in the right position then its not theoretical as scotty mac said. Some times (like when i went to college) they gave me a cheap ethernet cord which was a cat cord, and when you looked at the rj45 on the end it only had the 2 pairs going into it.

scotty says that ther eis unrated cable out there that may look like cat3 and cat5, etc cable, but is not marked as rated. those are a crap shoot then, they may suffer in performance or not.

as i said, very rarely is gear just 100 bt, it is almost all 10/100bt, which means you can just plug it in abd play despite what cmet said

 

[spidey07]

I guess just to clarify - if indeed it is category 3 cable then by all means you can run 10 Base-T on it.

You will have to force the network cards to 10 Mbs and Full duplex however otherwise they'll negotiate to 100/full and you "could" have serious performance problems. You never know until you try however...if the cable is very short it might run 100 Base-T just fine.

 

[nbarb99]

Heh, for the sake of science and geeklyness, I tried this yesterday, and it WORKED

I had a computer in another room that needed a 10Mbps connection (the NIC was not a 10/100, older ISA model) so I grabbed an unused "junk" phone cable and tried to figure out a way to plug it into the RJ-45 port(s).
It seems RJ-11 ends will fit fine into RJ-45 ports, but the pins are in the wrong place for Ethernet. (Only the middle four pins are "connected" if you plug an RJ-11 end into an RJ-45 port)

I don't have a crimper, so I couldn't mod my own RJ-45 ends onto the telephone cable.. time to improvise! Ran off to Altex and grabbed 2 nice CAT5 crossover adapters. They have an RJ-45 port on one side and a built-in plug on the other, so all I needed to do was open it up and switch a few pins around on the port side.

The pin-switching hack was painless, it seems these crossover adapters were made for this project The adapter just snaps apart and you can rewire the pins with ease.

Anyway, I hacked/modded both the adapters and plugged them in.. no signal. Oops, they're crossover adapters I grabbed another crossover adapter I had to reverse the crossover switching (didn't want to invert the pins on one of my hacked modules just yet) and my goodness, it worked!!

I ran a throughput test and I get about 8.3~8.5Mbps, just about what I'd expect. I didn't try and be daring with a 100Mbps test, because that NIC doesn't support 10/100