[Peon]

My ESXi box (a Dell C1100) comes with 2 Ethernet ports, but I can't think of a usage for the second port. At one point I thought about separating the VMs from the management interface, but given that both ports are plugged into the same switch and therefore share the same upstream link, I can't see any benefits to doing so, and thus the second port remains unused...

 

[GoodPurpose]

If your VM's don't need separated networks and if they are both plugged into an unmanaged switch the only two reasons could be load balancing or using it as a back-up port for management.