Image Change Triggers for build not working for dockerStrategy

Issue

• I have a base image created out of rhel7:latest and I created child image from base image and I implemented the build trigger for base image but I could not get child image build triggered when I build base image.

• I tried from document as described here : https://docs.openshift.com/enterprise/3.1/dev_guide/builds.html#image-change-triggers

spec:
  triggers:
    -
      type: ConfigChange
    -
      type: ImageChange
      imageChange:
        lastTriggeredImageID: '172.30.x.x:5000/demo/base-image:latest'

....

 strategy:
    type: Docker
    dockerStrategy:
      from:
        kind: DockerImage
        name: '172.30.x.x:5000/demo/base-image:latest'

• Is this trigger also work for external images ( not built within same openshift ) for example available on Redhat ?