Slow upload speed in macOS guests with vmxnet3 network adapter in VMware Fusion

Products

• VMware Desktop Hypervisor

Issue/Introduction

This article provides a workaround to the slow upload speed issue seen in macOS guests like (Ventura/Monterey) with vmxnet3 network adapter.

Symptoms:
macOS Guests created in VMware Fusion with Ethernet adapter configured as vmxnet3 in x86 macbooks showing slow upload speed

Resolution

MacOS guests uses apple’s vmxnet3 driver. Currently, there is no resolution.

Workaround:
As a workaround for this issue, VMware recommends to disable TSO in macOS guests.

By default TSO will be on.
sudo sysctl -a | grep net.inet.tcp.tso

Run the below command in macOS guests to turn off TSO
sudo sysctl -w net.inet.tcp.tso=0

To have any sysctl setting stick between restarts:

create a file /etc/sysctl.conf and add a below entry
net.inet.tcp.tso=0