Beacon Probing Considerations and risks

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VMware vSphere ESXi

This article provides information on risks when using an unsupported configuration for Beacon Probing.

VMware ESX

Beacon probing is intended and designed as network detection and failover mechanism.
Each pNIC in a team sends and listen Beacon probe packets to detect failures on upLink connectivity .
It is required to have 3 or more pNICs to detect a failure on one of them. If only two NICs are assigned and one of them loses connectivity, the switch cannot determine which NIC needs to be taken out of service because both do not receive beacons as a result all packets sent to both uplinks
VMware does not recommend multiple physical NIC connections to the same physical Switch. This can cause Beacon probing to fail to detect issues beyond the switch.

Use 3 or more nics with beacon probing since with 2 the host cannot definitively determine which NIC has failed.

Risks and Behaviors with 2 NICs configured with Beacon Probing:

If one link fails, the host cannot determined which one is failed that leads to undefinened condition and as a result all packets sent to both uplinks

Considerations:

You can enable beacon probing when downstream link failures may impact availability and there is no Link State Tracking on the physical switch/vmnics.
Beacon probing requires at least three NICs to function correctly
We do not recommend multiple physical NIC connections to the same physical Switch. This can cause Beacon probing to fail to detect issues beyond the switch.

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