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?

Answer 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).

Answer 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.

Answer 3

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.

Answer 4

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.

Answer 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    

Answer 6

TL;DR there's no substitute for trying. It may, or may not work. If it works, hurrah. Practice > Theory.

Leaving this for posterity. The number of twists is often exaggerated (as in importance) as I have none for the 2 phone lines running from point A to B. This is as voice grade as it gets. A lot of "you need at minimum Cat 5" talk about standards has been off-putting until actually trying. Fishing a wire is impossible in my case without a lot of complex building work.

For short enough runs, it may be fine. As usual, with any non-standard setup, YMMV. I've been running 100baseT full-duplex over a pair of phone wires for year and a half. Wired according to TIA/EIA 568B for the first 2 pairs. The actual throughput is around 95 Mbps with absolutely no packet loss:

1175 packets transmitted, 1175 received, 0% packet loss, time 1199966ms
rtt min/avg/max/mdev = 0.273/0.400/1.215/0.048 ms

While streaming video (Netflix, Amazon, television, etc.) isn't that taxing, I've been also gaming over this setup via Steam Link / Steam Remote Play which is both latency and throughput sensitive. No issues whatsoever. Beats powerline every day of the week and twice on Sunday.

To make matters worse, the network is spliced in a couple of places using junction boxes (that kind you'd normally punch in with a Krone tool) as the phone lines lacked the length to actually reach the wall sockets I installed on both ends. Because of the wall sockets, I'm using bog standard ethernet cables to connect to the rest of the network.

Now, bear in mind, the distance is short: ~10m phone wires + 2m splices + 4m of ethernet cables to connect the switches. There isn't a continuous piece of wire, but: cat 5e + wall socket + cat 5e (2 pairs used) + junction box + 2 phone lines (1 cable, not twisted, lots of crosstalk I'd imagine) + junction box + cat 5e (2 pairs used) + wall socket + cat 5e.

Answer 7

I know this is a old thread, But for others how may still need to use RJ11 jack and wiring for Ethernet RJ45 purpose it will work. See if you have a existing phone line wiring running through your place that has a RJ11 four wire setup, then this is all you need. With RJ45 Ethernet you only use 4 wires in the cable for transmission of data required for internet. You can buy RJ11 to RJ45 conversion cables to use from the outlets or you can wire up your own outlets to be RJ45. As long as the wires that go in are connected the same on the other end, then you will have no problem. I wired up my friends place using the RJ11 Phone wiring and he has 100mbps from the ISP and now has 89mbps at the outlets.