The management switch provides Out-Of-Band (OOB) connectivity to the baseboard management controller (BMC) on each server.
The management network fabric does not carry vSphere management, vSAN, or vMotion traffic. That traffic resides on the network fabric created by the ToR and inter-rack switches. As a result the management switch is a non-redundant component in the physical rack. If this switch goes down, some functionality such as monitoring may not be available until it comes back up. Workloads will continue to run, but the infrastructure associated with them cannot be modified or controlled.