The health check support in vSphere Distributed Switch 5.1 and later helps you identify and troubleshoot configuration errors in a vSphere Distributed Switch.

Use vSphere Distributed Switch health check to examine certain settings on the distributed and physical switches to identify common errors in your environment's networking configuration. The default interval between two health checks is 1 minute.

Important: Use health check to troubleshoot network problems, and then disable it after you identify and resolve the problem. After you disable vSphere Distributed Switch health check, the generated MAC addresses age out of your physical network environment according to your network policy. For more information, see Knowledge Base article KB 2034795.
Configuration Error Health Check Required Configuration on the Distributed Switch
The VLAN trunk ranges configured on the distributed switch do not match the trunk ranges on the physical switch. Checks whether the VLAN settings on the distributed switch match the trunk port configuration on the connected physical switch ports. At least two active physical NICs
The MTU settings on the physical network adapters, distributed switch, and physical switch ports do not match. Checks whether the physical access switch port MTU jumbo frame setting based on per VLAN matches the vSphere distributed switch MTU setting. At least two active physical NICs
The teaming policy configured on the port groups does not match the policy on the physical switch port-channel. Checks whether the connected access ports of the physical switch that participate in an EtherChannel are paired with distributed ports whose teaming policy is IP hash. At least two active physical NICs and two hosts

Health check is limited to only the access switch port to which the distributed switch uplink connects.