Node:
Status NetworkUnavailable: True
Message error:
RouteController failed to create a route
Try delete the node and create new node. After create new node status returned to normal.
How to troubleshoot or check problem
In order to get more info from your problem you can retrieve logs from StackDriver--> Logging --> Loggs viewer, user "Advanced Filter" and there search by "Status NetworkUnavailable: True Message error" or "RouteController failed to create a route"