上文提到，docker的网络模式一共有五种，birdge 、host 、overlay、nacvlan、none、Network plugin 六种模式，这里主要介绍网桥（bridge）默认桥接模式。

一、简介

在网络概念中，桥接网络是一种链路层设备，它在网络段之间转发通信。网桥是运行在主机内核上的一个硬件设备或者软件设备。在docker中，桥接网络是使用软件桥接，连接到同一桥接网络上的容器直接可相互通信，而且是全端口的，而与未连接到该桥接网络的容器直接隔离，如此，桥接网络管理同一主机上所有容器的连接与隔离。docker的桥接驱动程序自动在主机上安装规则，同一网桥上的网络可相互通信，不同网桥网络容器相互隔离。

桥接网络适用于同一主机docker daemon生成的容器，对于不同主机daocker daemon的容器间交互，要么使用操作系统级的路由操作，要么使用overlay网络驱动。

当我们启动docker时，systemctl start docker，一个默认的桥接网络（birbr0）将自动被创建,连接docker daemon 与宿主机器，同时创建一个网络docker0,后续生产的容器将自动连接到该桥接网络（docker0）上。我们可查看本地网桥 , 每创建一个容器，将新建一个桥接，连接容器与默认的桥接网络。

[[email protected] hadoop]# brctl show
bridge name     bridge id               STP enabled     interfaces
docker0         8000.0242b47b550d       no
virbr0          8000.52540092a4f4       yes             virbr0-nic
[[email protected] hadoop]#

网桥 virbr0 连接docker0与宿主机器，在网桥上创建了接口virbr0-nic，该接口接收docker0网络的数据。每生成一个容器，在docker0上新建一个接口，并且docker0的地址被设置成容器的网关。

[[email protected] hadoop]# docker run --rm -tdi nvidia/cuda:9.0-base 
[[email protected] hadoop]# docker ps
CONTAINER ID        IMAGE                  COMMAND             CREATED             STATUS              PORTS               NAMES
9f9c2b80062f        nvidia/cuda:9.0-base   "/bin/bash"         15 seconds ago      Up 14 seconds                           quizzical_mcnulty
[[email protected] hadoop]# brctl show
bridge name     bridge id               STP enabled     interfaces
docker0         8000.0242b47b550d       no              vethabef17b
virbr0          8000.52540092a4f4       yes             virbr0-nic
[[email protected] hadoop]#

查看本地网络信息 ifconfig -a

[[email protected] hadoop]# ifconfig -a
docker0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.0.1  netmask 255.255.240.0  broadcast 192.168.15.255
        inet6 fe80::42:b4ff:fe7b:550d  prefixlen 64  scopeid 0x20<link>
        ether 02:42:b4:7b:55:0d  txqueuelen 0  (Ethernet)
        RX packets 37018  bytes 2626776 (2.5 MiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 46634  bytes 89269512 (85.1 MiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

eno1: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.252.130  netmask 255.255.255.0  broadcast 192.168.252.255
        ether 00:25:90:e5:7f:20  txqueuelen 1000  (Ethernet)
        RX packets 14326014  bytes 17040043512 (15.8 GiB)
        RX errors 0  dropped 34  overruns 0  frame 0
        TX packets 10096394  bytes 3038002364 (2.8 GiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
        device memory 0xfb120000-fb13ffff  

eth1: flags=4099<UP,BROADCAST,MULTICAST>  mtu 1500
        ether 00:25:90:e5:7f:21  txqueuelen 1000  (Ethernet)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 0  bytes 0 (0.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
        device memory 0xfb100000-fb11ffff  

lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
        inet 127.0.0.1  netmask 255.0.0.0
        inet6 ::1  prefixlen 128  scopeid 0x10<host>
        loop  txqueuelen 0  (Local Loopback)
        RX packets 3304  bytes 6908445 (6.5 MiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 3304  bytes 6908445 (6.5 MiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

oray_vnc: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1200
        inet 172.1.225.211  netmask 255.0.0.0  broadcast 172.255.255.255
        ether 00:25:d2:e1:01:00  txqueuelen 500  (Ethernet)
        RX packets 1944668  bytes 227190815 (216.6 MiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 2092320  bytes 2232228527 (2.0 GiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

vethabef17b: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet6 fe80::e47d:4eff:fe87:39d3  prefixlen 64  scopeid 0x20<link>
        ether e6:7d:4e:87:39:d3  txqueuelen 0  (Ethernet)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 8  bytes 648 (648.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

virbr0: flags=4099<UP,BROADCAST,MULTICAST>  mtu 1500
        inet 192.168.122.1  netmask 255.255.255.0  broadcast 192.168.122.255
        ether 52:54:00:92:a4:f4  txqueuelen 0  (Ethernet)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 0  bytes 0 (0.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

virbr0-nic: flags=4098<BROADCAST,MULTICAST>  mtu 1500
        ether 52:54:00:92:a4:f4  txqueuelen 500  (Ethernet)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 0  bytes 0 (0.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

docker 结合网桥与路由规则，设置同一宿主机器内，各容器间交互，docker 容器桥接网络驱动下，网络接入方式如下图所示：

docker网络模式之 default bridge模式一、简介二、容器间访问配置

如果启动容器时，指定了端口映射，将内部端口 80 映射到主机端口8080，也可0.0.0.0：8080方式，指定网卡，如下

docker run --rm -ti -p 8080:80  nvidia/cuda:9.0-base

然后查看路由表，

iptables -t nat -vnL

可看到增加了路由转发规则：

[[email protected] hadoop]# iptables -t nat -vnL
Chain PREROUTING (policy ACCEPT 55 packets, 2470 bytes)
 pkts bytes target     prot opt in     out     source               destination         
 161K 8056K PREROUTING_direct  all  --  *      *       0.0.0.0/0            0.0.0.0/0           
 161K 8056K PREROUTING_ZONES_SOURCE  all  --  *      *       0.0.0.0/0            0.0.0.0/0           
 161K 8056K PREROUTING_ZONES  all  --  *      *       0.0.0.0/0            0.0.0.0/0           
    0     0 DOCKER     all  --  *      *       0.0.0.0/0            0.0.0.0/0            ADDRTYPE match dst-type LOCAL

Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
 pkts bytes target     prot opt in     out     source               destination         

Chain OUTPUT (policy ACCEPT 0 packets, 0 bytes)
 pkts bytes target     prot opt in     out     source               destination         
 3442  258K OUTPUT_direct  all  --  *      *       0.0.0.0/0            0.0.0.0/0           
    0     0 DOCKER     all  --  *      *       0.0.0.0/0           !127.0.0.0/8          ADDRTYPE match dst-type LOCAL

Chain POSTROUTING (policy ACCEPT 0 packets, 0 bytes)
 pkts bytes target     prot opt in     out     source               destination         
    0     0 MASQUERADE  all  --  *      !docker0  192.168.0.0/20       0.0.0.0/0           
    0     0 RETURN     all  --  *      *       192.168.122.0/24     224.0.0.0/24        
    0     0 RETURN     all  --  *      *       192.168.122.0/24     255.255.255.255     
    0     0 MASQUERADE  tcp  --  *      *       192.168.122.0/24    !192.168.122.0/24     masq ports: 1024-65535
    0     0 MASQUERADE  udp  --  *      *       192.168.122.0/24    !192.168.122.0/24     masq ports: 1024-65535
    0     0 MASQUERADE  all  --  *      *       192.168.122.0/24    !192.168.122.0/24    
 3442  258K POSTROUTING_direct  all  --  *      *       0.0.0.0/0            0.0.0.0/0           
 3442  258K POSTROUTING_ZONES_SOURCE  all  --  *      *       0.0.0.0/0            0.0.0.0/0           
 3442  258K POSTROUTING_ZONES  all  --  *      *       0.0.0.0/0            0.0.0.0/0           
    0     0 MASQUERADE  tcp  --  *      *       192.168.0.3          192.168.0.3          tcp dpt:80

Chain DOCKER (2 references)
 pkts bytes target     prot opt in     out     source               destination         
    0     0 RETURN     all  --  docker0 *       0.0.0.0/0            0.0.0.0/0           
    0     0 DNAT       tcp  --  !docker0 *       0.0.0.0/0            0.0.0.0/0            tcp dpt:8080 to:192.168.0.3:80

默认的端口类型为 TCP。

二、容器间访问配置

首先启动两个容器，然后进入到容器内，查看个容器IP信息，

[[email protected] hadoop]# docker ps
CONTAINER ID        IMAGE                  COMMAND             CREATED             STATUS              PORTS                  NAMES
462751a70444        nvidia/cuda:9.0-base   "/bin/bash"         17 minutes ago      Up 17 minutes       0.0.0.0:8080->80/tcp   sad_heyrovsky
9f9c2b80062f        nvidia/cuda:9.0-base   "/bin/bash"         41 minutes ago      Up 41 minutes                              quizzical_mcnulty
[[email protected] hadoop]#

我这里启动两个容器，然后调用 docker inspect 容器ID 查看容器IP

docker inspect -f {{.NetworkSettings.IPAddress}} 容器ID

我们这两个容器为 192.168.0.2 192.168.0.3

进入其中的一个容器, ping 另外一台机器，会发现，仅仅只能采用地址模式才能ping的通 ping 192.168.0.3,

docker exec -ti 9f9c2b80062f /bin/bash

如果采用在/etc/hosts内追加别名，然后ping 名字，发现无法ping通。

192.168.0.3 node1

至于原因，下篇将继续讲解用户自定义桥接网络，解决该问题。

docker网络模式之 default bridge模式一、简介二、容器间访问配置

一、简介

二、容器间访问配置

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