During the replacement of some VMware ESXi hosts at a customer, I discovered a recurrent failure of the vSphere Distributed Switch health checks. A VLAN and MTU mismatch was reported. On the physical side, the ESXi hosts were connected to two HPE 5820 switches, that were configured as an IRF stack. Inside the VMware bubble, the hosts were sharing a vSphere Distributed Switch.
The switch ports of the old ESXi hosts were configured as Hybrid ports. The switch ports of the new hosts were configured as Trunk ports, to streamline the switch and port configuration.