Below is my VirtualService YAML. If I don't comment the below-marked line (subset: v1) then any request fails with "no healthy upstream".

Any idea, why this could be an issue?

apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: dragon-vs
  namespace: flight
spec:
  hosts:
  - "*" 
  gateways:
    - dragon-gateway
  http:
  - match:
    - uri:
        prefix: /api/values
    route:
    - destination:
        host: dragon.flight.svc.cluster.local
        subset: v1 ## !!! this is the problem !!! ## 
      weight: 95
    - destination:
        host: dragon.flight.svc.cluster.local
        subset: v2
      weight: 5