Running Ethernet over two phone lines

Question

I am trying to run Ethernet through my house along existing phone wires. I had originally planned to use the phone wires to pull the cat5e cable, but it appears the phone lines are stapled to studs somewhere. From questions like this one, I know I can use the cable to get 100M at best because there are only 3 pairs, and gigabit requires 4 pairs.

However, I am fortunate enough to have two phone lines that run parallel that I can use. This gives me a total of 6 pairs. I know the phone wires still have higher crosstalk, but would combining the two help? Could I get gigabit speeds? How should I match the phone line pairs to the Ethernet pairs?

Solution 1

Your existing voice grade phone wiring is probably no better than Cat3, if even that. So you'd probably struggle to get 10BASE-T to work, and 100 mbps and Gigabit Ethernet is probably out of the question.

10BASE-T (10mbps) was the last widely-available flavor of Ethernet that was designed to work over Cat3 voice grade wiring. So assuming your existing phone wiring is even Cat3 (note: untwisted telephone line cords are not), and if you have two pair, you could possibly use them for 10mbps Ethernet.

What's commonly called "100BASE-T" is actually "100BASE-TX", which requires two pair of Cat5. There were two competing IEEE standards for 100 mbps Ethernet over unshielded twisted pair (UTP) wiring, but they were never widely deployed: 100BASE-T4 (required 4 pairs of Cat3) and 100BASE-T2 (required 2 pairs of Cat3). I don't think you can find any 100BASE-T4 or 100BASE-T2 NICs or hubs/switches anymore, because you could barely find them when they were new in the 1990's.

Gigabit Ethernet (1000BASE-T) requires 4 pairs of Cat5.

The IEEE stopped caring about voice grade wiring after 100BASE-TX was a huge market success while 100BASE-T{2,4} flopped.

I suppose it's possible that given a short enough run of Cat3 that you could get lucky and happen to get 100BASE-TX or 1000BASE-T to work, but it seems unlikely to me. I think there's a decent chance you could make 10BASE-T work, but even that isn't guaranteed without knowing for sure that you have good Cat3 end-to-end, and you're wiring it like Ethernet (point to point) and not like home phone wiring (which often has branches or multiple jacks on a long passive bus).

Solution 2

I currently have 10baseT running on telephone wiring that predates the cat3 spec by 5 years (cable says it was made in 1987 by Essex -- obviously prior to their merger with Superior and forming what we know today as Superior-Essex) and that is at distances approaching or exceeding the 358 foot / 100 meter limit. None of these 10baseT runs are showing any errors in the switch.

Many of these runs have two cross-connects and four 66 blocks on them.

My suggestion---give it a try. It will likely work at 10baseT speeds but you must set the speed at either the switch or computer end; autonegotiation will try to make it work at 100baseT or even gigabit speeds, which is probably not going to work very well over existing telephone wire.

Solution 3

You can get 1 GB over short distances of Cat 3. I had my house wired with 8 conductor Cat 3 in 1994. I have been able to upgrade most of the house to 1 GB speed using all 4 pairs. The furthest terminations (100') only acheive 100 mb, while terminations under 90' seem to be able support a stabel 1 GB connection.

Solution 4

I have seen 10baseT run over two old crappy pair of phone lines, with multiple junctions, likely most a 100 meters, all over a building. It worked fine for years - probably still is.

At both ends was a generic 5 port 10baseT Ethernet switch, nothing special.

This wiring should work.

Solution 5

You need 4 pairs for gigabit. Gigabit uses all 4 pairs.

If you want to try to wire the 2 pairs required for 10/100, follow this pinout.

Looking at the bottom of the cable (clip tab on the top), pin 1 is on the left.

Here's the wiring table from the above link:

TIA/EIA 568B wiring table:

Name    Pin     Cable Color         Pin     Name
TX+     1       White/Orange        1       TX+
TX-     2       Orange              2       TX-
RX+     3       White/Green         3       RX+
        4       Blue                4    
        5       White/Blue          5    
RX-     6       Green               6       RX-
        7       White/Brown         7    
        8       Brown               8    

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Comments

[sawdust]

The proper way to run Ethernet over voice-grade copper is to use xDSL. That's essentially the reason why telcos developed the various flavors of xDSL. There are point-to-point setups that could do what you want. See this answer. If cost is an issue, than used telco stuff could work.

[sawdust]

The problem is bandwidth (or lack of it with voice-grade copper compared to CAT5) rather than simply the number of conductors.

[tanius]

Exactly what you say about autonegotiation. This setup did not work stable for me until I forced it to be recognized as 10 Mbit/s Ethernet by adding a legacy old 10BASE-T switch on one end. (There was no way to just configure the speed in my router or software.)