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I am new to Vmware Esxi and im doing testing for an experiment with an Vmware ESXI 6.0.0 server. on the server there is two Ubuntu guest clients with one VMXNET3 each, both on the same Vswitch.

Upon doing an IPerf3 from Ubuntu A to Ubuntu B with the following command:

iperf -c Ubuntu B -u -b 80m -t 100 -V

I get a package loss of 10% on all my packets. It is not a stable packet loss as it jumps up as high as 50% from times. Testing different speeds yields the similar result. The Esxi monitor shows a total cpu load of 24% so it seems not to be of cpu overuse.

I have followed these pages to try fix the problem;


Increased the RX buffer https://www.itechlounge.net/2015/05/linux-how-to-tune-up-receive-tx-and-transmit-rx-buffers-on-network-interface/

Increased MTU size. This helped slightly with greater packet amounts but small amounts of data still yields high packetloss (10%~ packetloss). http://www.ubuntugeek.com/how-to-change-mtu-maximum-transmission-unit-of-network-interface-in-ubuntu-linux.html

Changed MTU size on the Vswitch. https://docs.vmware.com/en/VMware-vSphere/5.5/com.vmware.vsphere.networking.doc/GUID-40856C1E-7631-4228-A111-13A783316595.html


What can I do more to troubleshoot my VMware ESXI setup?


  • what model are the physical nics? have you updated their firmware? are you using native nic drivers (preferred) rather than the vmklinux driver? – Mark Wagner May 2 '18 at 23:07
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    FYI: Traffic between virtual machines connected in the same vSwitch, port group and VLAN doesn't transit the host NIC. – joeqwerty May 3 '18 at 11:22
  • Let us have as much detail about the VSS/VDS as possible please – Chopper3 May 3 '18 at 11:52
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After testing also to upgrade vmwaretools to latest, same symptoms was there. I then tried upgrading my whole Vmware setup. Upon upgrading to vmware esxi 6.5 The packetloss problems dissapeared.

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Consider that iperf and UDP at high bitrates (80M is high in this regard) are susceptible to being broke, in my experience.

Also increase TX buffer if you want to continue.

Iperf3 in tcp mode will show you retransmits. If the retransmits is 0, you didn't have any packet loss.

See what the machine can do on itself; ie iperf -c and -s on same machine. Whatever you get there, you won't exceed when you actually traverse the network.

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