docker默认提供3种网络模式：bridge桥接模式、host主机模式、none无网络模式
可以通过命令 docker network ls 查看
1.1、bridge桥接模式
桥接模式是docker默认的网络模式。当docker服务启动后，会创建一个名字叫docker0的虚拟网桥，然后选一个与宿主机不一样的网络ip地址以及子网分配给docker0
另外每创建一个容器就会新增一个容器网卡，然后以桥接方式架到docker0网桥中，docker0会以NAT地址转换的方式通过宿主机的网卡，从而与公网进行通信。
如下图所示：
下面进行测试演示：
1、启动docker服务后，通过命令 ip addr 发现docker0网卡ip为172.17.0.1
2、启动一个docker容器 docker run -itd centos:7 /bin/bash ，再进行一次 ip addr
发现新增一个网卡veth506a249@if6
3、执行命令 yum install -y bridge-utils 安装工具，使用命令 brctl show 查看一下桥接情况
可以看到容器的网卡桥接到docker0上
1.2、host主机模式
主机模式是指docker容器与公网通信时使用的是宿主机的ip与端口，同时容器自己不会有ip地址，所以在这模式下容器与宿主机之间并没有隔离很分明。
在容器启动命令时用参数--net=host指定当前容器网络模式 docker run -itd --net=host centos:7 /bin/bash
1.3、none无网络模式
无网络模式下相当于容器处于断网状态下，同样没有自己的ip地址。
创建容器时通过参数 --net=none 设置，这比较少使用。
1.4、总结
上面讲了关于docker的网络模式，主要关于以哪种方式让服务器内部的容器与公网进行通信。
1、假如使用的是默认的桥接网络模式，启动容器的时候需要使用参数--p 宿主机端口:容器端口设置端口的映射。
2、假如使用的是host主机模式，因为使用的是宿主机的ip与端口，那就直接可以与公网通信。
二、Docker的内部通信
在实际的项目环境中，肯定会存在多个服务间通信的情况。也就是多个容器之间通信。
下面了解的是关于一个宿主机下多个服务间通信的情况。
举个例子，例如多个服务访问一个mysql数据库。通常只需要在多个服务之间配置数据库的地址就可以了。
因为它们都是通过默认的bridge进行通信的。
现在启动两个服务centos01和centos02
[root@localhost ~]# docker run -itd --name=centos01 mycentos:nettools /bin/bash 982a3d4cdb131bf33d217218c04aad278ac762376337e4180fd2eadc63599541 [root@localhost ~]# docker run -itd --name=centos02 mycentos:nettools /bin/bash e1c43e2000915b8256b1f0b6793b6f4bd1b2ff33ae1f32c6872ce21d4c5c8e4e
查看一下centos02的ip地址 docker inspect e1c43e2000915 ，发现是172.17.0.3
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