I allocated a block of time tonight for hacking something but failed to do it. The work got longer than usual and I came home late. Turn on the virtual machine running systemd, I saw the internet stop working. I just switch my windows host from using wireless to stable ethernet cable. Something I don't know changes and it breaks the network setting.
I tried to several internet setting but it turned out the problems is more fatal than I thought. I tried google for hints but all I got is some people with the similar problems to mine. In despair, I try adding a new network card and to my surprise the new network card works. I ping-ed google and saw the response.
The problem solved with me having no idea why it works.
Anyway systemd is different with tradition initd and it takes time to unlearn some concepts in initd before really getting used to systemd.