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I was recently provided with a 2018 MBP by my employer. The network throughput slows gradually until I'm forced to reboot.


The following machines are connected via wired ethernet to a gigabit switch:

  • 2018 MBP (the problematic machine, 10.14.4)
  • 2015 MBP (the control, thunderbolt ethernet adapter, 10.14.4)
  • 2010 iMac (the test target, built in ethernet, ubuntu)

The 2018 MBP has a usbc-thunderbolt adapter, with a thunderbolt display attached and the ethernet cable connected to the display.

When the throughput drops, I've tried the following:

  • Switch to WiFi - doesn't help, speed starts off around 300MBit/s but drops to the level the wired connection is currently at.
  • Use a different switch port / ethernet cable - doesn't help
  • Test speed on control MBP using 2018 MBP's ethernet cable & switch port (it's fine)
  • Connect thunderbolt monitor to control MBP and test throughput (also fine)
  • Disconnect usbc-thunderbolt adapter incase it's doing something odd (no difference)
  • Disconnect power from 2018 MBP (no difference)
  • Sleep/Wake 2018 MBP (no difference)

I setup a test to show the problem: rebooted the 2018 MBP then looped iPerf making connections to the iMac and plotted the results, sure enough after a couple of days I'm getting 10MBits/s across a gigabit switch:

throughput vs time graph

The problem isn't the iMac (test target) as I also made periodic tests from the control MBP to the iMac which consistently showed ~940Mbits/s.

I've been using the 2015 MBP and thunderbolt display with it's ethernet connection for years without issue, and have ruled that out as a cause. Also WiFi shows the same problem, which suggests its not related to a specific interface. I suspect a software problem with the networking stack on the 2018.

Potentially suspicious software:

  • Symantec Endpoint Protection (mandated by employer)
  • Pulse Secure (required for VPN connection to employer, but not connected during these tests)
  • Docker (required for development, does add bridges etc to local networking - this doesn't cause a problem on the 2015 MBP though.)


  1. Any idea what this might be about?
  2. Is there any way to reset the networking stack or some workaround that doesn't involve a reboot?

Unfortunately removing SEP is not an option :(

marked as duplicate by Community Jun 5 at 14:35

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  • You mention sleep/wake, presume you have the power plugged in whilst this test is ongoing so that there's no potential power throttling? – FiddleDeDee May 31 at 7:55
  • Yep, power was connected the entire time, apart from when I disconnected the power for a short time to check it wasn't a bad supply. – Hugh Saunders May 31 at 7:56
  • Reset PRAM? I know it's a new machine, but won't hurt to try. – FiddleDeDee May 31 at 8:04
  • Tried resetting the PRAM, long shot, but no difference. – Hugh Saunders Jun 3 at 13:38
  • Another person with the same issue: apple.stackexchange.com/questions/359723/… – Hugh Saunders Jun 5 at 10:45

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