Enabling vSphere Distributed Switch Health Check in the vSphere Web Client

The network configuration for the vSphere infrastructure is a two-step process, whereby users must configure the physical network switches to which the vSphere host is connected and then configure the VDS. There are key network parameters, such as VLAN, network adapter teaming, and MTU, that should be configured properly on physical and virtual switches. 

However, there are occasions when there are network connectivity issues in the user environment because these parameters are not configured properly. Network connectivity issues caused by configuration errors are often difficult to identify. This particularly is the case in an organization where the network administrators and vSphere administrators take management ownership of physical network switches and vSphere hosts respectively. In earlier versions of vSphere, there were no tools available that could help resolve such misconfigurations across the physical and virtual switches.

Source: http://kb.vmware.com/kb/2032878