015docker默认bridage模式详解

一、

当Docker进程启动时,会在主机上创建一个名为docker0的虚拟网桥,此主机上启动的Docker容器会连接到这个虚拟网桥上。虚拟网桥的工作方式和物理交换机类似,这样主机上的所有容器就通过交换机连在了一个二层网络中。

从docker0子网中分配一个IP给容器使用,并设置docker0的IP地址为容器的默认网关。在主机上创建一对虚拟网卡veth pair设备,Docker将veth pair设备的一端放在新创建的容器中,并命名为eth0(容器的网卡),另一端放在主机中,以vethxxx这样类似的名字命名,并将这个网络设备加入到docker0网桥中。可以通过brctl show命令查看。

bridge模式是docker的默认网络模式,不写--net参数,就是bridge模式。使用docker run -p时,docker实际是在iptables做了DNAT规则,实现端口转发功能。可以使用iptables -t nat -vnL查看。

bridge模式如下图所示:

015docker默认bridage模式详解

#我本地启动了2个容器
docker pull ubuntu
docker pull nginx

root@arun:~# docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
e81696ccf7db ubuntu "bash" 16 minutes ago Up 16 minutes ubuntu-default
64e678f0dc2e nginx "/docker-entrypoint.…" 49 minutes ago Up 49 minutes 80/tcp nginx-default

#(2)从宿主机上看
#其中的docker0为网桥,ens33是vm的网卡,最后的两个veth即为两个容器对应的在docker0上的虚拟网卡,如上图所示;
root@arun:~# ifconfig
docker0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 172.17.0.1  netmask 255.255.0.0  broadcast 172.17.255.255
        inet6 fe80::42:79ff:fe9e:56d1  prefixlen 64  scopeid 0x20<link>
        ether 02:42:79:9e:56:d1  txqueuelen 0  (Ethernet)
        RX packets 17271  bytes 730406 (730.4 KB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 17954  bytes 47369915 (47.3 MB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

ens33: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.31.95  netmask 255.255.255.0  broadcast 192.168.31.255
        inet6 fe80::20c:29ff:fed0:2fa9  prefixlen 64  scopeid 0x20<link>
        ether 00:0c:29:d0:2f:a9  txqueuelen 1000  (Ethernet)
        RX packets 113793  bytes 141872357 (141.8 MB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 42423  bytes 3327679 (3.3 MB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

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 1000  (Local Loopback)
        RX packets 292  bytes 27086 (27.0 KB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 292  bytes 27086 (27.0 KB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

veth9151ca7: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet6 fe80::98f7:91ff:fe22:cf0e  prefixlen 64  scopeid 0x20<link>
        ether 9a:f7:91:22:cf:0e  txqueuelen 0  (Ethernet)
        RX packets 12356  bytes 677385 (677.3 KB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 12517  bytes 36370839 (36.3 MB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

vetha32505c: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet6 fe80::c8c2:b6ff:fee4:38cd  prefixlen 64  scopeid 0x20<link>
        ether ca:c2:b6:e4:38:cd  txqueuelen 0  (Ethernet)
        RX packets 4915  bytes 294815 (294.8 KB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 5468  bytes 11001466 (11.0 MB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

* 可以从docker网络设备管理看出,都哪些容器插到了bridge docker0上:

root@arun:~# docker network ls
NETWORK ID     NAME      DRIVER    SCOPE
405a37e19268   bridge    bridge    local
3a788fcf07b7   host      host      local
ab45462b6b41   none      null      local
#从以下可以看到有哪两个容器连接到了bridage0上:
root@arun:~# docker network inspect 405a37e19268
        "Containers": {
            "64e678f0dc2e27041c5d0f329a485c4b1d0585e9a9f4db6e6b51de10f08d66d7": {
                "Name": "nginx-default",
                "EndpointID": "ac7df1259dc70e52f45946d6905510909b27c2681cacb5ea43b7d33194b95dd6",
                "MacAddress": "02:42:ac:11:00:02",
                "IPv4Address": "172.17.0.2/16",
                "IPv6Address": ""
            },
            "e81696ccf7db9a1fbd3ea199afa7b646fdcd82b1431a387264cdbafd0ad5be7a": {
                "Name": "ubuntu-default",
                "EndpointID": "a8befcf9167c7433a985dee31eef23cf2024c04de8da100ffefbfb27439ac9ec",
                "MacAddress": "02:42:ac:11:00:03",
                "IPv4Address": "172.17.0.3/16",
                "IPv6Address": ""
            }
        },
        "Options": {
            "com.docker.network.bridge.default_bridge": "true",
            "com.docker.network.bridge.enable_icc": "true",
            "com.docker.network.bridge.enable_ip_masquerade": "true",
            "com.docker.network.bridge.host_binding_ipv4": "0.0.0.0",
            "com.docker.network.bridge.name": "docker0",
            "com.docker.network.driver.mtu": "1500"
        },
        "Labels": {}
    }
]

 

#Reference: https://segmentfault.com/a/1190000040335988 

 

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