Ubuntu双网卡主机给其他主机共享网络

1. 设备：
   1. Ubuntu主机(主机1)有两张网卡：eno1(外网), eno2(内网)
   2. 其他主机(主机2)有一张网卡：eno1(连接第一台主机的eno2)
2. 目标：

   • 主机1给主机2共享网络。

   • 步骤：

     1. 配置主机1的两张网卡：

        推荐使用netplan。

        example:

        # Let NetworkManager manage all devices on this system
        network:
        version: 2
        #  renderer: NetworkManager
        renderer: networkd
        ethernets:
             eno1:
                     addresses: [192.168.3.50/24]
                     gateway4: 192.168.3.1
                     dhcp4: no
                     nameservers:
                             addresses: [114.114.114.114]
                     optional: true
             eno2:
                     addresses: [192.168.0.1/24]
                     gateway4: 192.168.3.50
                     dhcp4: no
                     nameservers:
                             addresses: [114.114.114.114]
                         optional: true
        

     2. 开启主机1ipv4转发：

        sudo vim /etc/sysctl.conf
        /ipv4.ip_forwar                 # 直接回车
        ^                               # 到行首
        x                               # 删除`#`
        :wq                             # 保存并退出
        

     3. 开启主机1包过滤：

        sudo iptables -P INPUT ACCEPT
        sudo iptables -P FORWARD ACCEPT
        sudo iptables -t nat -A POSTROUTING -s 192.168.0.0/24 -o eno1 -j MASQUERADE
        sudo service networking restart
        

        最后一行一定写对，前面ip/mask是子网的网段/掩码，-o指向输出端口(外网网卡)

        sudo iptables-save > /etc/iptables.rules        # 保存
        sudo iptables-restore < /etc/iptables.rules     # 恢复
        

     4. 主机2网卡配置：

        # Let NetworkManager manage all devices on this system
        network:
          version: 2
          #  renderer: NetworkManager
          renderer: networkd
          ethernets:
                  eno1:
                          addresses: [192.168.0.x/24]   # x in [2,254]
                          gateway4: 192.168.0.1         # eno2的ip address
                          dhcp4: no
                          nameservers:
                                  addresses: [114.114.114.114]
                          optional: true
        

     5. 配置生效：两主机都要执行

        sudo netplan try
        sudo netplan apply