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What is beacon probing? (1005577)

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Purpose

This article provides information on beacon probing.

Resolution

How does beacon probing work?

Beacon probing is a network failover detection mechanism that sends and listens for beacon probe packets on all physical NICs in the team. In a teamed uplink packets will be sent through each physical NIC.

Note: In ESXi 5.x and 6.x beacon packets are sent every 1 seconds. For more information, see the Edit the Teaming and Failover Policy on a Standard Port Group in the vSphere Web Client section in the vSphere Networking Guide.

Beacon probing detects failures, such as cable disconnects and physical switch power failures on the physical network. It uses this packet information along with link state to determine link failure. The design of Beacon probing works with physical Switch redundant networking to determine downstream link failures beyond the ESXi host networking. 
  • VMware recommends having 3 or more physical NICs in the team.
  • 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.
For example:

 
 

In the above example, all the physical NICs have a discrete path to the distributed switch. When the failure happens at a distribution switch level, beacon probing will detect this failure due to the uplink on the ESXi host that connects to the failed distributed switch will not receive the beacon probe packets.

Below are the configurations which are NOT Recommended:

Configuration 1:


Configuration 2:


Note: Since Beacon probing intends and design for network redundancy to detect network failover for teaming, each pNICs in a team send out and receive Beacon probe packet to make sure that the connections/Links are working fine. Thus, we recommend to have 3 or more pNICs to prevent split brain condition and works more accurate network failure detection. However, we do not recommend multiple pNICs connect to pSwitch. It is because once Beacon probing detects the failure at distribution switch,the Beacon probe packets can transmit in the pSwitch. So it is meaningless to have Beacon probing in this situation. Please see the not recommended layout with multiple pNICs and pSwitches as example.

When should you enable beacon probing?
You must enable beacon probing when downstream link failures may impact availability and there is no Link State Tracking on the physical switch.

Additional Information

For more information, see:

Beacon probing utilizes virtual MAC addresses to check the link status of each VLAN and determine link failure for physical NICs in a vSwitch team. You may see entries for virtual MAC address in the esx.conf file and the MAC address table of your physical switch. For more information, see:

See Also

Update History

11/11/2013 - Added ESXi 5.5 to Product Versions. 05/08/2015 - Added ESXi 6.0 to Product Versions.

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