why lo0.0 has a ip of128.116.20.xx in vMX by default? it could be deleted even deleting lo0.0. Thanks.
Do You have configuration group called "global"?
You have to de-apply it
delete apply-groups global
Or You can de-apply it to lo0 only:
set interfaces lo0 apply-groups-except global
This configuration group provides some defaults like router-id/SSH enable/ etc. If You de-apply it altogether, You have to reconfigure everything manually under respective hierarchies.
Thanks a lot for your help. I deleted the ip of 128.116.20.xx with "delete groups global interfaces lo0.0 family inet" so that the route table is much clean when doing exercises.