Controller Disconnected Operation (CDO) mode ensures that the data plane connectivity is unaffected when hosts lose connectivity with the controller. You can enable CDO mode to avoid temporary connectivity issues with the controller.
You can enable CDO mode for each host cluster connected to a transport zone. CDO mode is disabled by default.
When CDO mode is enabled, NSX Manager creates a special CDO logical switch, one for every transport zone. The VXLAN Network Identifier (VNI) of the special CDO logical switch is unique from all other logical switches. When CDO mode is enabled, one controller in the cluster is responsible for collecting all the VTEP information reported from all transport nodes, and replicating the updated VTEP information to all other transport nodes. When a controller fails, a new controller is elected as the new master to take the responsibility and all transport nodes connected to the original master are migrated to the new master and data is synced between the transport nodes and the controllers.
If you add a new cluster to a transport zone, NSX Manager pushes the CDO mode setting and the VNI to the newly added hosts. If you remove the cluster, NSX Manager removes the VNI data from the hosts.
When you disable CDO mode on a transport zone, NSX Manager removes the CDO logical switch from the controller.
In a Cross-vCenter NSX environment, you can enable CDO mode only on the local transport zones or in a topology where you do not have any local transport zones and have a single universal transport zone for the primary NSX Manager. CDO mode gets replicated on the universal transport zone for all secondary NSX Managers.
You can enable CDO mode on local transport zone for a secondary NSX Manager.