When using the VMXNET3 driver on ESXi 4.x, 5.x, 6.x, you see significant packet loss during periods of very high traffic bursts
This issue occurs when packets are dropped during high traffic bursts. This can occur due to a lack of receive and transmit buffer space or when receive traffic which is speed-constrained. For example, with a traffic filter.
To resolve this issue, ensure that there is no traffic filtering occurring (for example, with a mail filter). After eliminating this possibility, slowly increase the number of buffers in the guest operating system.
To reduce burst traffic drops in Windows Buffer Settings: