Rollback is enabled by default. However, you can enable or disable rollbacks at the vCenter Server level.
Several networking events can trigger a rollback. The events are grouped into these categories:
Host networking rollbacks occur when an invalid change is made to the host networking configuration. Every network change that disconnects a host also triggers a rollback. These changes to the host networking configuration are examples of what might trigger a rollback:
Several networking events can trigger a rollback. The events are grouped into these categories:
- Host networking rollbacks (virtual switches or network system)
- Distributed switch rollbacks
Source: VMware KB 2032908
Host Networking Rollbacks
Host networking rollbacks occur when an invalid change is made to the host networking configuration. Every network change that disconnects a host also triggers a rollback. These changes to the host networking configuration are examples of what might trigger a rollback:
- Updating the speed or duplex of a physical NIC
- Updating DNS and routing settings
- Updating teaming and failover policies or traffic shaping policies of a standard port group that contains the management VMkernel network adapter
- Updating the VLAN of a standard port group that contains the management VMkernel network adapter
- Increasing the MTU of management VMkernel network adapters and its switch to values not supported by the physical infrastructure
- Changing the IP settings of management VMkernel network adapters
- Removing the management VMkernel network adapter from a standard or distributed switch
- Removing a physical NIC of a standard or distributed switch containing the management VMkernel network adapter
If a network disconnects for any of these reasons, the task fails and the host reverts to the last valid configuration.
Distributed Switch Rollbacks
Distributed switch rollbacks occur when invalid updates are made to distributed switch-related objects, such as distributed switches, distributed port groups, or distributed ports. These changes to the distributed switch configuration might trigger a rollback:
Distributed switch rollbacks occur when invalid updates are made to distributed switch-related objects, such as distributed switches, distributed port groups, or distributed ports. These changes to the distributed switch configuration might trigger a rollback:
- Changing the MTU of a distributed switch
- Changing the following settings in the distributed port group of the management VMkernel network adapter
- Teaming and failover
- VLAN
- Traffic shaping
- Blocking all ports in the distributed port group containing the management VMkernel network adapter
- Overriding the policies above for the distributed port to which the management VMkernel network adapter is connected
If an invalid configuration for any of the changes occurs, one or more hosts might be out of synchronization with the distributed switch.
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