mac无法ping通vagrant的私有网络ip的解决办法

1. 确保virtualbox拥有两张网卡：

   1. 一张用作网络地址转换(NAT)；
   2. 一张用作private_network，即 仅主机(hostOnly)网络；
2. 选择其中一张网卡，假如这张网卡的ipv4地址为 192.168.57.1，那么你就可以从
   192.168.57.11 到 192.168.57.255的范围选择一个作为private_network；

3. 假如我选择了 192.168.57.15作为 private_network，那么 Vagrantfile就修改为：

   # 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. 重启两次虚拟机后，登录虚拟机，就可以通过命令 ip addr查看到你设置的 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

   这个时候，基本就可以从主机ping通vagrant虚拟机了。

另外，为了防止访问虚拟机里面的服务而出现以下问题：

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

建议关闭防火墙：

$ sudo systemctl status firewalld.service # 查看得到“active（running）”，表示防火墙已经被打开了
$ sudo systemctl stop firewalld.service # 关闭防火墙
$ sudo systemctl disable firewalld.service # 永久关闭防火墙