Azure 似乎有随机改变虚拟机硬件配置的习惯，不告诉用户任何事情。
这当然在文档中提到过，虽然有些含糊：
Can I manually assign IP addresses to NICs in virtual machines?
No. You must not change any interface properties of VMs. Any changes may lead to
potentially losing connectivity to the virtual machine.
和：
Will the MAC address remain the same for my virtual machine once it has been created?
No. A virtual machine’s MAC address can change for a few different reasons. If the
VM is put in the status Stopped (Deallocated), …