slow network speed issue vmxnet3 ?


Active Member
Apr 12, 2016
ok.. researched this up and down.. sideways and have tried everything

napp-it esxi all - in - on setup


2x vmxnet3 adapters with .conf modified with 4096 and lso disabled

ubuntu 1 e1000 and 1 vmxnet3

debian 1 vmxnet3

on ubuntu I am getting slow iperf3 to napp-it... over the vmxnet3 network.

on the e1000 adapter I get about 8Gbits with the vmxnet3 I get 2.5Gbits

if I do the iperf3 from napp-it to ubuntu I get 7.8Gbits and running iperf3 -R I get 11.1

running an iperf3 from debian to either napp-it or ubuntu I get about 11 Gbits

so why is running iperf3 from ubuntu to napp-it .. only over vmxnet3 adapter slow?


Well-Known Member
Dec 31, 2010
Good question that I cannot answer as I do not use this combination.
The default tcp and vmxnet3 values are optimized for 1G so the basic tuning is to increase tcp and vmxnet3 buffers, optionally use Jumboframes for 10G+, sometimes LSO is an item, You can also try Open-VM tools (OmniOS/OI repo) or the generic Vmware tools. Sometimes like with Windows you must tune client settings for best performance (ex deactivate interrupt throttling on Windows)