1. 確保virtualbox擁有兩張網卡：

   1. 一張用作網絡地址轉換(NAT)；
   2. 一張用作private_network，即 僅主機(hostOnly)網絡；
2. 選擇其中一張網卡，假如這張網卡的ipv4地址為 192.168.57.1，那麼你就可以從
   192.168.57.11 到 192.168.57.255的範圍選擇一個作為private_network；

3. 假如我選擇了 192.168.57.15作為 private_network，那麼 Vagrantfile就修改為：

   # vi: set ft=ruby :
   
   # All Vagrant configuration is done below. The "2" in Vagrant.configure
   # configures the configuration version (we support older styles for
   # backwards compatibility). Please don't change it unless you know what
   # you're doing.
   Vagrant.configure("2") do |config|
    
     config.vm.box = "centos7-box"
   
     config.vm.network "private_network", ip: "192.168.57.15"
   
     config.vm.synced_folder "../data", "/vagrant_data" 
   
   end

4. 重啓兩次虛擬機後，登錄虛擬機，就可以通過命令 ip addr查看到你設置的 private_network：

     enp0s8: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
    link/ether 08:00:27:4f:ad:ae brd ff:ff:ff:ff:ff:ff
    inet 192.168.57.15/24 brd 192.168.57.255 scope global enp0s8
       valid_lft forever preferred_lft forever
    inet6 fe80::a00:27ff:fe4f:adae/64 scope link
       valid_lft forever preferred_lft forever

   這個時候，基本就可以從主機ping通vagrant虛擬機了。

另外，為了防止訪問虛擬機裏面的服務而出現以下問題：

curl: (7) Failed connect to 192.168.57.15:8080; Connection refused

建議關閉防火牆：

$ sudo systemctl status firewalld.service # 查看得到“active（running）”，表示防火牆已經被打開了
$ sudo systemctl stop firewalld.service # 關閉防火牆
$ sudo systemctl disable firewalld.service # 永久關閉防火牆