ESXi 7.0 – VM to VM network speeds capped at 1Gb when using 10Gb (Different hosts)


Before I assume something is wrong with my switch, I wanted to see if anyone had any troubleshooting tips to try.

I have two ESXi hosts connected over SFP+ on a Unifi switch and recently noticed that I can no longer get 10Gb speeds when going to a VM on one host to another. Unfortunately I only noticed this after upgrading to 7.0 so I am not sure this is the culprit.

When I run an iPerf test from VM1 on ESXi 1 to VM2 on ESXi2, speeds are capped at 1Gb (e.g. 883 Mbits/sec). However, speeds are fine if running from VM to VM on the same host (e.g. 7.87 Gbits/sec).

I have switched cables, double checked my switch settings (nothing has changed), updated NIC firmware etc. There are no 1Gb cables connected at the time to neither ESXi host to rule out traffic going over 1Gb.

Any ideas what else to try?

p.s. I had posted a similar question earlier but decided to delete it and provide more information/things I tried.

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