A week ago a colleague contacted me about the fact that he had issues with load balancing on “Virtual Port ID”. Only a single NIC was utilized while running over 10 VMs on a single host. When changing the order of the NICs the traffic would flip over but again no load balancing. I remembered a KB article from months ago and pointed him to the article. Yesterday on the VMTN Community someone reported a similar issue with his ESX 3.5 environment. I referred to the article again and it solved the problem. Might be worth checking your setup in terms of load balancing. Is your second NIC actually being used? And if not here’s a short description of the problem and the solution:

Source

• Symptom: NIC Teaming load balancing properties do not take effect with global vSwitch configuration settings.
• Resolution: Override the load balancing order at the port group level, under Policy Exceptions, select the checkbox and choose the proper load balancing from the dropdown menu. Please note that this workaround only works until the next reboot of ESX.