Phone Line in place of ethernet?

Oct 24, 2018
Hello all. I'm posting this because I've yet to find it answered else where. This is my first post anywhere, I hope I'm in the right category.

Am I able to use the red, green, black, and yellow copper in pins 1,2,3, and 6 of an rj45 to feed a switch in my utility until I'm able to pull a cat5e in its place? I'm aware it's not the professional way to do it, but I just want to know if it will work at the least.

I moved into a new house recently. I have a fair amount of experience working with cat5e and I was looking to make all the cat5e outlets in my house active. The house is already wired. The room with my modem does not have a cat5e outlet, but the room adjacent to it does. All I'd have to do is drill a line from one room to the other, run it under the carpet to the other side of the room, and pop it in the outlet to feed the rest of the cat5 in the utility room.

Or so I thought.

I popped the wallplate off the other room, and instead of cat5e I found some older 2 pair phone lines. My masterplan had been soiled.

However, as I learned more about how rj45s work, I learned that it technically only uses 4 pins (1,2,3, and 6), unless you've got a gigabit service.

The way I see it, copper is copper. And while I know it might not be the proper way to do it, I'm just looking to set wallfishing a new cat5e aside for another 6 months or so. And copper in the phone lines are solid, so that's a plus. Speeds out of my modem are 400 mbps.


Aug 18, 2006
you can do 100 with 1,2,3,6 but copper is not copper ethernet is twisted pair. The twist is the key. there are 4 pairs and only 2 are used in 100 whereas 1000 uses all 4 pair.


Mar 16, 2013

Gigabit performance, within your house LAN, is the base standard today.
Your router, your NIC in the PC, any switch you might buy...all gigabit.

"copper is copper" ?
No. Twist matters.
Using phone line, you get, at best, 1/10 that speed.

"Speeds out of my modem are 400 mbps. "
That would be the advertised WiFi speed? Irrelevant for a wired connection.
The LAN ports are almost certainly gigabit.
See if you can read the jacket and read the cat type. Then google it's rated performance. cat5 or cat5e can hit 100Mbs with 4 wires.
If you're lucky they can cat5e and it's intact if you haven't checked already.
If it's untwisted too far it won't work.