Unable to get Ethernet connection on three Macbooks

"Regular" telephone wire is Category 3, which will work at modest distances. But as already mentioned, you must use the 8-position RJ45 connectors, wired correctly, to get the conductors lined up properly.

Those should not be a problem. Cables made from Category 5, 5e, 6, and 6e wire have their pairs differentially twisted to reduce crosstalk and are good for up to 100 meters. Those are rated for Gigabit speeds, which says they have all 8 conductors present and wired correctly.

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1000 speed "Gigabit Ethernet" uses the wiring COMPLETELY differently, so some users find that cables that worked fine for 100 stop working when asked to run at Gigabit Ethernet speeds.

I discovered that 8-wire exception experimentally after a very frustrating late night debugging session. I was so mad, I promptly cut the ends off each and every 4-wire Ethernet cable I could get my hands on, and used the bulk wire for ty-wraps.

<< Do I need something more than a standard ADSL RJ11 to RJ11 cable (which is what I have two of)? >>

Yes, you do indeed. You need cables with 8-position RJ45 connectors, wired for Ethernet. If the cables are over about 100 feet, you may get better results from category-5 or 5e cables or better, which have the pairs twisted at different rates to minimize crosstalk and noise between pairs. Total length per cable is limited to 100 meters (about 300 feet).

If you would ever like to go faster than 100, they must have all eight conductors present and wired correctly for Ethernet connection.

Hey Dave King2,

We understand that you're unable to connect three different MacBook Pro devices to the internet via Ethernet. You've taken some great steps with your devices already.

Check out these articles on how to connect a Mac via Ethernet:

• Connect to the Internet or a network using Ethernet (for macOS High Sierra)
• Connect your Mac to the internet using Ethernet (for macOS Catalina)

The information below from this article might also be helpful: Connect to the internet with your Mac

"Connect using Ethernet

To use a wired connection to the internet, connect an Ethernet cable between your router or modem and the Ethernet port on your Mac. Some Mac models require an Ethernet adapter, such as the Belkin USB-C to Gigabit Ethernet Adapter or the Apple Thunderbolt to Gigabit Ethernet Adapter."

As for you question about a different cable, you could always try another type of cable to see if that may help since this issue is happening with multiple MacBook Pro devices. Another step you can also take to isolate this issue further, is to try to connect to Ethernet via a test user on one of your devices: Set up users, guests, and groups on Mac

Take care.

In network preferences make sure the Ethernet connection is at the top of the list. Otherwise if WiFi is at the top of the list it will use that connection and not even try the lower in the list Ethernet connection.

Before easy access to the Internet, companies would lease a dedicated phone line from the phone company, conditioned for low noise for data, and set up modems on each end. I worked for a company that leased dozens of lines to remote sites.

When these lines had troubles, it was often caused by corrosion on the terminals at one of the many, many connection points along the way. Because they were data circuits, they did not "Ring", and corrosion had a chance to accumulate. When the technicians would go to investigate, they would typically apply 90 volts from a test battery they carried, and in most cases, the line would "come clear with test battery". In many cases, that was all that was needed to keep them working... for a while.

Grant Bennet-Alder wrote:

<< Do I need something more than a standard ADSL RJ11 to RJ11 cable (which is what I have two of)? >>

Yes, you do indeed. You need cables with 8-position RJ45 connectors, wired for Ethernet. If the cables are over about 100 feet, you may get better results from category-5 or 5e cables or better, which have the pairs twisted at different rates to minimize crosstalk and noise between pairs. Total length per cable is limited to 100 meters (about 300 feet).

If you would ever like to go faster than 100, they must have all eight conductors present and wired correctly for Ethernet connection.

Good catch Grant. I missed the fact he is using the wrong cables.

4-position RJ-11 plugs will center themselves in the 8-position RJ-45 jack. Ethernet up to 100 does not use the center two conductors at all, because they might be a telephone connection.

Telephone connection can provide + and - 48 Volts at 5 Hz for Ringing. That would not be good for your Ethernet gear.