Network failure detection is used to determine the liveliness of a physical uplink using one of two mechanisms—link status only or beacon probing:

• Link status only is used to determine the connectivity status of the physical uplink, which could have encountered a NIC failure, a cable disconnect, and so on.
• Beacon probing is used to determine an upstream network failure. For more information on beacon probing, read VMware Knowledge Base article 100577 at https://kb.vmware.com/kb/1005577.