Belkin F2CU040 Random Drop Out - M1 Max 16" MacBook Pro

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Belkin F2CU040 Random Drop Out - M1 Max 16" MacBook Pro

Been having difficulty with latest macOS Monterey version 12.1 - 12.3 and getting reliable connectivity using the Apple USBC to Gigabit Ethernet Adapter (Belkin F2CU040).

Adapter can be plugged in and services brought online and it may operate for a period of time but the adapter will randomly just drop out and connectivity disappears. If you open a Terminal prompt and attempt to ping any destination, including the default gateway, it fails.

It's necessary to unplug the adapter, then plug it back in again for macOS Monterey to sync back up and re-establish a connection. It has been happening frequently and does not matter which USBC port that it is connected to. Have also tried a second F2CU040 adapter and problem remains.

If you have another USBC device connected, such as an iPhone on an alternative USBC port, and the F2CU040 gets into this condition, you can simply unplug the other USBC port connecting the iPhone and it can clear the condition allowing the F2CU040 to start working again. Problem has been occurring on Monterey 12.1 and all of the recent updates including the latest 12.3 release.

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The problem was happening so frequently that it was impacting daily work and normal operation of the system, so a replacement USBC to Gigabit Ethernet adapter from Lention Model CU604 E was selected. The Lention device works reliably and has been operating for an extended period of time without failure and does not matter if other USBC devices are plugged into the system.

Feedback assistant was utilized, logs taken and provided to Apple but no resolution at this time.

MacBook Pro

Posted on Mar 22, 2022 11:35 PM

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Answer 1

Mar 27, 2022 8:44 AM in response to sieversjr

You answered your own question. The problem is with the Belkin F2CU040 adapter including a second identical one. When you substituted an alternate adapter (Lention Model CU604 E ) it started working reliably. Replace the Belkin adapters they are not working. You should contact Apple Support directly about this issue.

These forums are hosted by Apple for the benefit of Apple customers helping Apple customers but official contact with Apple is not found here.

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Answer 2

Mar 28, 2022 2:40 AM in response to sieversjr

Yes Ive noticed this too its been driving me crazy.

Other than removing and re-inserting the dongle, this seems to work from the CLI. Ive also noticed it gets very hot.

 sudo ifconfig en6 down
 sudo ifconfig en6 up

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Answer 3

sieversjr Author

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11 points

Apr 15, 2022 5:43 AM in response to James Brickley

Well it turns out it didn't solve the problem - Happens on both hardware adapters and even on the latest release of macOS 12.3.1. I can reproduce the problem and think if I did appropriate debug logging/captures it could be provided to Apple developers to solve the problem.

Where is the proper place to get items such as this filed officially and have you done this before?

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Answer 4

sieversjr Author

Level 1

11 points

Apr 28, 2022 6:46 AM in response to sieversjr

Have been working with AppleCare/Apple Engineers on this problem - taking captures and uploading to their engineering team and they are making progress and doing a good job to understand the issue. Discovered some interesting results here that I thought might be worth mentioning for everyone's benefit.

Through multiple test scenarios, we discovered that some common applications such as VPN / Security software may install extensions which appear under System Preferences -> Network. On the MBP 16" M1Max, when using the Wireless subsystem which is a discrete chipset (not part of SoC M1Max), everything works under load for extended periods of time without issue. When these extensions need to operate with Wired Ethernet adapter and the macOS Thunderbolt4/USBC subsystem/drivers there have been some issues identified and they are investigating the logs/captures.

If the extensions are not utilized, extensive tests under load show the Thunderbolt4/USBC subsystem/drivers and the Wired adapters work properly and have no issue. This is helping to identify the root cause of the potential problem and the engineering folks are investigating to see why the extensions working fine with Wireless but seem to encounter periodic reliability issues when interfacing with macOS subsystems for Thunderbolt4/USBC. Starting to get closer to an answer which should help get the problems resolved and into the next release for everyone.

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Answer 5

Apr 28, 2022 10:31 AM in response to sieversjr

New Information:

Check your System Information details, Apple menu -> About this Mac -> System Report -> Ethernet

USB 10/100/1000 LAN:

Bus: USB

Vendor Name: Realtek

Product Name: USB 10/100/1000 LAN

Vendor ID: 0x0bda

Product ID: 0x8153

USB Link Speed: Up to 5 Gb/s

Driver: com.apple.DriverKit.AppleUserECM <--- This is the problem...

Apple is using the generic ECM driver (DriverKit.AppleUserECM) because Realtek hasn't provided Apple a compatible driver for newer macOS versions and especially not an ARM64 Apple Silicon compatible one. It should look something like this, com.realtek.driver.AppleRTL815XEthernet if it was using a vendor supplied driver.

If you look for 2.5Gbps USB-C to Ethernet adapters most of those use a better supported Intel chipset. Such as CalDigit. Broadcom chipsets appear to also see better macOS support.

This is a HUGE problem due to the vast number of RealTek Ethernet 8153 chipsets found in most dongle and dock products on the market. This problem was recently discussed on the ATP podcast episode 478. It's been mentioned on HackerNews and there's a gist on GitHub discussing the problem in great detail. From my perspective, it appears to be more of a Realtek problem than an Apple one.

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Belkin F2CU040 Random Drop Out - M1 Max 16" MacBook Pro

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