When you upgrade a group of Cisco vBond Orchestrator, Cisco vSmart Controllers, and Cisco IOS XE SD-WAN devices or Cisco vEdge devices in either a standalone or Cisco vManage cluster deployment, the software upgrade and reboot is performed first on the Cisco vBond Orchestrator, next on the Cisco vSmart Controller, and finally on the Cisco IOS XE SD-WAN devices or Cisco vEdge devices. https://www.cisco.com/c/en/us/td/docs/routers/sdwan/configuration/Monitor-And- Maintain/monitor-maintain-book/maintain.html