Energy Efficient Ethernet - How to tell it's on, and what may be breaking your network

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Level 1

9 points

Energy Efficient Ethernet - How to tell it's on, and what may be breaking your network

Either my network switches, or my router, or both, all of which are autoconfigured to their maximum of 2.5GigE, have problems with energy-efficient-ethernet.

Macs enable this by default, and this only became a problem when I got a Mac mini with a 10GigE adapter to at least be able to use 2.5G.

This setting is now hidden somewhat. It shows under the Hardware media "Duplex" option, which you can change when you use Manual mode and set the link speed manually. Unfortunately, due to a bug that exists all the way up to macOS Sequoia and possibly beyond, this field in the dialog will only show "full-duplex" on open, instead of whatever it was last configured to.

You may check the current setting by opening Terminal.app and running:

```

ifconfig | grep media:

```

Feel free to configure it to "full-duplex,flow-control", which is defaults minus "energy-efficient-ethernet", if you experience the frequent connection drops associated with the link speed dropping to 10Mbit, assuming your switches or router aren't EEE compliant.

Mac mini, macOS 15.6

Posted on Aug 18, 2025 10:54 PM

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Answer 1

Old Toad

Level 10

214,314 points

Aug 19, 2025 11:08 AM in response to kode54

What is the advertised speed of your internet connection, i.e. what speed are you paying for?

I assume from your post that your Mac Mini is connected to the router with an ethernet cable, right?

I had the same problem that I was paying for a 500 MBs internet speed but was only getting 100 MBs. The problem was the Cat 5 cable that was connecting my Mini to my router. It was only rated for 100 MBs. I changed it for the a Cat 6 cable and was immediately running at. 500 MBs up and down on the internet.

Also don't run any VPN apps as they can affect internet speed. Unless you're using a true VPN tunnel, such as between you and your employer's, school's or bank's servers, they provide false security from a privacy standpoint. Read these articles: Pubic VPN's are anything but private and Security Risks: The Dangers of Using Free VPNs (eccu.edu).

Additionally a new study ("Apple Offers Apps With Ties to Chinese Military”) is specifically about VPN apps in Apple’s App Store.

Check your cable.

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Answer 2

kode54 Author

Level 1

9 points

Aug 20, 2025 05:41 AM in response to Old Toad

My cables are all Cat6. They're fine. I get the advertised speed. The problem is, with EEE enabled, connections like rsync tasks will drop after about 10 seconds.

It's not the cable. It's the switch. And I'm not buying super expensive gear just so Apple can make my Mac save a little energy.

Edit: From my Linux desktop, in the same room, on the same switch:

EEE settings for enp16s0:

EEE status: enabled - active

Tx LPI: 5 (us)

Supported EEE link modes: 100baseT/Full

1000baseT/Full

2500baseT/Full

Advertised EEE link modes: 100baseT/Full

1000baseT/Full

2500baseT/Full

Link partner advertised EEE link modes: 100baseT/Full

1000baseT/Full

2500baseT/Full

Looks like the switch doesn't support 10baseT/Full, which the Mac apparently tries to negotiate and fails.

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