Intermittent packet loss on M1 iMac ETHERNET adapter

We have many 2022 M1 iMacs that are experiencing intermittent packet loss (up to 80% sometimes).

WiFi is turned off, IPV6 is set to local-link, Switch and router all function properly. Cables all test good. We are using Monterey because OS X Ventura breaks our software so I am not able to do an update.

When the problem occurs, I plug in a USB-C Ethernet adapter and take the same ethernet cable from the Power Brick, plug it into the USB-C Ethernet adapter and network is 100% Stable and packet loss is zero.

I can duplicate the problem by trying to transfer a file to another machine on the network, or doing a download. Sometimes it only transfers about 10MB of a 700MB file then stalls and all the network apps start to time out and fail. JUST ON THAT MAC. Switching to the USB adapter fixes the problem. Doesn't matter if the iMac is set to use DHCP or a Static IP address.

This is happening to all of our M1 iMacs intermittently. And it's usually one or two iMacs at a time.

It seems that there are lots of people reporting this issue, but no one has a real solution other than using an external Ethernet Adapter. So I think it's a bug. Unfortunately the Apple Feedback page just kind of tells you to take a long walk on a short pier.

Posted on Jan 23, 2023 11:17 AM

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6 replies

hcsitas

Level 6

13,964 points

Jan 24, 2023 8:45 AM in response to Spencerator

That’s the problem - anything over 10’ is inviting trouble from Macs even if the cables are fully tested. Use switches to extend.

den.thed

Level 10

89,350 points

Jan 23, 2023 1:36 PM in response to Spencerator

Could be the Cat rating of your local Ethernet network.

I would test a Cat 6e cable between the Ethernet Switch and the Ethernet connection on the iMac’s power brick.

Then if that doesn’t help, I would test a Cat 6e cable between the router and the Ethernet connection on the iMac’s power brick.

Spencerator Author

Level 1

62 points

Jan 24, 2023 8:41 AM in response to den.thed

We are using CAT6 and the first thing we did was test the cables. We replaced several of them for good measure because of the intermittent nature of the packet loss. We also suspected the RJ45s in the power bricks were not making a good connection.

Just to make it clear, this problem is occurring intermittently on at least 7 of our 13 M1 iMacs. The Intel iMacs that are on the same network have zero packet loss. Replacing cables has had no effect. Using an external Ethernet adapter with the M1s solves the issue and results in zero packet loss.

I'm thinking that there is either some kind of bug in the network stack, the RJ45s in the power bricks are poor or there is an intermittent connection in the mag-safe cable between the iMac and the power brick.

hcsitas

Level 6

13,964 points

Jan 23, 2023 1:49 PM in response to Spencerator

How long’s the cable?

Spencerator Author

Level 1

62 points

Jan 24, 2023 8:42 AM in response to hcsitas

Cables run anywhere from 30 to maybe 50 feet.

den.thed

Level 10

89,350 points

Jan 24, 2023 10:40 AM in response to Spencerator

Give Official Apple Support a call and see what they recommend.

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Intermittent packet loss on M1 iMac ETHERNET adapter