Questions

what determines which uplink is used when a failover event occurs?

When an explicit failover order has not been configured on a virtual switch with multiple
uplinks, what determines which uplink is used when a failover event occurs?

A.
The uplink with the shortest route

B.
The next available uplink on the list

C.
The reported uptime for the surviving uplinks

D.
The first available uplink that reports a positive Link State

Explanation:
Networking Virtual Machines Jon Hall Technical Trainer, VMWORLD 2006, slide 27.

Failover is implemented by the VMkernel based upon configurable parameters

1. Failover order: Explicit list of preferred links (uses highest-priority link which is up)
2. 1. Maintains load balancing configuration
2. Good if using a lower bandwidth standby NIC
3. Rolling failover — preferred uplink list sorted by uptime [C above]
The uplink with the shortest route – all uplinks are on the same network and so have the
same route [A is incorrect]
The next available uplink on the list has not been defined if explicit failover order is not
selected [B is incorrect]

Discussion

2 Responses to “what determines which uplink is used when a failover event occurs?”

  1. salman says:

    Answer B is correct.

    From the VMware VCP5 training manual: “VMware vSphere: Install, configure, Manager” Vol1 page 183, paragraph 1 states “When using explicit failover order, always use the highest order uplink from the list of active adapters that pass failover-detection criteria.”

    • rajen says:

      Yes Salman,
      “When using explicit failover order, always use the highest order uplink from the list of active adapters that pass failover-detection criteria”.

      But the question says explicit failover order is not configured, if there is no available next uplink, how it will select the highest uplink?

      So may be it goes on Rolling failover… I Think “C” is correct

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