跨主机网络方案包括：
docker原生的overlay和macvlan。
第三方方案：常用的包括flannel、weave 和 calico。
[root@linux-node1 ~]# docker run -d -p 8500:8500 -h consul --name consul progrium/consul -server -bootstrap
[root@linux-node1 ~]# netstat -tulnp |grep 8500
tcp6 0 0 :::8500 :::* LISTEN 61092/docker-proxy-
容器启动后，可以通过 http://192.168.56.110:8500 访问 Consul。
接下来修改 node1 和 node2 的 docker daemon 的配置文件/var/lib/systemd/system/docker.service。
--cluster-store 指定 consul 的地址。
--cluster-advertise 告知 consul 自己的连接地址。
[root@linux-node1 ~]# cat /usr/lib/systemd/system/docker.service
......
ExecStart=/usr/bin/dockerd-current --add-runtime docker-runc=/usr/libexec/docker/docker-runc-current --default-runtime=docker-runc --exec-opt native.cgroupdriver=systemd --userland-proxy-path=/usr/libexec/docker/docker-proxy-current --seccomp-profile=/etc/docker/seccomp.json --cluster-store=consul://192.168.56.110:8500 --cluster-advertise=eth0:2376 $OPTIONS ......
[root@linux-node1 ~]# systemctl daemon-reload
[root@linux-node1 ~]# systemctl restart docker
node1 和 node2 将自动注册到 Consul 数据库中。
在 node1 中创建 overlay 网络 ov_net1：
[root@linux-node1 ~]# docker network create -d overlay ov_net1 #-d overlay 指定 driver 为 overaly。
[root@linux-node1 ~]# docker network ls #查看当前网络
NETWORK ID NAME DRIVER SCOPE
8eb7fd71a52c bridge bridge local
6ba20168e34f host host local
4e896f9ac4bc none null local
d9652d84d9de ov_net1 overlay global
[root@linux-node2 ~]# docker network ls #查看当前网络
NETWORK ID NAME DRIVER SCOPE
94a3bc259414 bridge bridge local
f8443f6cb8d2 host host local
2535ab8f3493 none null local
d9652d84d9de ov_net1 overlay global
node2 上也能看到 ov_net1。这是因为创建 ov_net1 时 node1 将 overlay 网络信息存入了 consul，node2 从 consul 读取到了新网络的数据。之后 ov_net 的任何变化都会同步到 node1 和 node2。
[root@linux-node1 ~]# docker network inspect ov_net1 #查看 ov_net1 的详细信息
[
{
"Name": "ov_net1",
"Id": "d9652d84d9de6d1145c77d0254c90164b968f72f2eda4aee43d56ab03f8530ed",
"Created": "2018-04-19T21:50:29.128801226+08:00",
"Scope": "global",
"Driver": "overlay",
"EnableIPv6": false,
"IPAM": {
"Driver": "default",
"Options": {},
"Config": [
{
"Subnet": "10.0.0.0/24",
"Gateway": "10.0.0.1"
}
]
},
"Internal": false,
"Attachable": false,
"Containers": {},
"Options": {},
"Labels": {}
}
][root@linux-node1 ~]# docker run -itd --name bbox1 --network ov_net1 busybox
340f748b06786c0f81c3e26dd9dbd820dafcdf73baa9232f02aece8d4c89a73b
[root@linux-node1 ~]# docker exec bbox1 ip r #查看容器的网络配置
default via 172.18.0.1 dev eth1
10.0.0.0/24 dev eth0 scope link src 10.0.0.2
172.18.0.0/16 dev eth1 scope link src 172.18.0.2
bbox1有两个网络接口eth0和eth1。eth0 IP为10.0.0.2，连接的是overlay网络ov_net1。eth1 IP 172.18.0.2，容器的默认路由是走eth1，eth1是哪儿来的呢？其实，
docker会创建一个bridge网络 “docker_gwbridge”，为所有连接到overlay网络的容器提供访问外网的能力。
[root@linux-node1 ~]# docker network ls
NETWORK ID NAME DRIVER SCOPE
8eb7fd71a52c bridge bridge local
751bd423a345 docker_gwbridge bridge local
6ba20168e34f host host local
4e896f9ac4bc none null local
d9652d84d9de ov_net1 overlay global
[root@linux-node1 ~]# docker network inspect docker_gwbridge
[
{
"Name": "docker_gwbridge",
"Id": "751bd423a345a7beaa6b4cbf2a69a7687e3d8b7e656952090c4b94aec54ec1b5",
"Created": "2018-04-21T16:11:57.684140362+08:00",
"Scope": "local",
"Driver": "bridge",
"EnableIPv6": false,
"IPAM": {
"Driver": "default",
"Options": null,
"Config": [
{
"Subnet": "172.18.0.0/16",
"Gateway": "172.18.0.1"
}
]
},
"Internal": false,
"Attachable": false,
"Containers": {
"340f748b06786c0f81c3e26dd9dbd820dafcdf73baa9232f02aece8d4c89a73b": {
"Name": "gateway_340f748b0678",
"EndpointID": "64cd599aaa2408ca0a1e595264e727b09d26482ba4d2aa18d97862ed29e23b51",
"MacAddress": "02:42:ac:12:00:02",
"IPv4Address": "172.18.0.2/16",
"IPv6Address": ""
}
},
"Options": {
"com.docker.network.bridge.enable_icc": "false",
"com.docker.network.bridge.enable_ip_masquerade": "true",
"com.docker.network.bridge.name": "docker_gwbridge"
},
"Labels": {}
}
]从
docker network inspect docker_gwbridge输出可确认docker_gwbridge的 IP 地址范围是172.18.0.0/16，当前连接的容器就是bbox1（172.18.0.2）。
而且此网络的网关就是网桥docker_gwbridge的IP 172.17.0.1。
[root@linux-node1 ~]# ifconfig docker_gwbridge
docker_gwbridge: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 172.18.0.1 netmask 255.255.0.0 broadcast 0.0.0.0
inet6 fe80::42:e4ff:feb8:22cb prefixlen 64 scopeid 0x20<link>
ether 02:42:e4:b8:22:cb 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
这样容器 bbox1 就可以通过 docker_gwbridge 访问外网。
[root@linux-node1 ~]# docker exec bbox1 ping -c 2 www.baidu.com
PING www.baidu.com (58.217.200.112): 56 data bytes
64 bytes from 58.217.200.112: seq=0 ttl=127 time=32.465 ms
64 bytes from 58.217.200.112: seq=1 ttl=127 time=32.754 ms
--- www.baidu.com ping statistics ---
2 packets transmitted, 2 packets received, 0% packet loss
round-trip min/avg/max = 32.465/32.609/32.754 ms[root@linux-node2 ~]# docker run -itd --name bbox2 --network ov_net1 busybox
[root@linux-node2 ~]# docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
68c81b90fb86 busybox "sh" 2 days ago Up 2 days bbox2
[root@linux-node2 ~]# docker exec bbox2 ip r
default via 172.18.0.1 dev eth1
10.0.0.0/24 dev eth0 scope link src 10.0.0.3
172.18.0.0/16 dev eth1 scope link src 172.18.0.2
##bbox2 IP 为 10.0.0.3，可以直接 ping bbox1
[root@linux-node2 ~]# docker exec bbox2 ping -c 3 bbox1
PING bbox1 (10.0.0.2): 56 data bytes
64 bytes from 10.0.0.2: seq=0 ttl=64 time=154.064 ms
64 bytes from 10.0.0.2: seq=1 ttl=64 time=0.789 ms
64 bytes from 10.0.0.2: seq=2 ttl=64 time=0.539 ms
--- bbox1 ping statistics ---
3 packets transmitted, 3 packets received, 0% packet loss
round-trip min/avg/max = 0.539/51.797/154.064 ms
docker会为每个overlay网络创建一个独立的network namespace，其中会有一个linux bridge br0，endpoint还是由veth pair实现，一端连接到容器中（即 eth0），另一端连接到namespace的br0上。
br0除了连接所有的endpoint，还会连接一个vxlan设备，用于与其他host建立vxlan tunnel。容器之间的数据就是通过这个tunnel通信的。逻辑网络拓扑结构如图所示：
不同的
overlay网络是相互隔离的。我们创建第二个overlay网络ov_net2并运行容器bbox3
[root@linux-node1 ~]# docker run -itd --name bbox3 --network ov_net2 busybox
946def609a7b183f68b8398b35fd3f72dc28bff47cc2ba63467f266fde297d5a
[root@linux-node1 ~]# docker exec -it bbox3 ip r
default via 172.18.0.1 dev eth1
10.0.1.0/24 dev eth0 scope link src 10.0.1.2 ##bbox3的ip为10.0.1.2
172.18.0.0/16 dev eth1 scope link src 172.18.0.4
[root@linux-node1 ~]# docker exec -it bbox3 ping -c 2 10.0.0.3 #bbox3无法ping通bbox2
PING 10.0.0.3 (10.0.0.3): 56 data bytes
^C
--- 10.0.0.3 ping statistics ---
2 packets transmitted, 0 packets received, 100% packet loss
如果要实现 bbox3 与 bbox2 通信，可以将 bbox3 也连接到 ov_net1。
[root@linux-node1 ~]# docker network connect ov_net1 bbox3
[root@linux-node1 ~]# docker exec -it bbox3 ping -c 2 10.0.0.3
PING 10.0.0.3 (10.0.0.3): 56 data bytes
64 bytes from 10.0.0.3: seq=0 ttl=64 time=34.110 ms
64 bytes from 10.0.0.3: seq=1 ttl=64 time=0.745 ms
--- 10.0.0.3 ping statistics ---
2 packets transmitted, 2 packets received, 0% packet loss
round-trip min/avg/max = 0.745/17.427/34.110 ms
docker默认为overlay网络分配 24 位掩码的子网（10.0.X.0/24），所有主机共享这个subnet，容器启动时会顺序从此空间分配IP。当然我们也可以通过--subnet指定 IP 空间。
[root@linux-node1 ~]# docker network create -d overlay --subnet 10.22.1.0/24 ov_net3a111191fa67e500015a2f3ab8166793d23f0adef4d66bfcee81166127915ff9f
[root@linux-node1 ~]# docker network ls
NETWORK ID NAME DRIVER SCOPE
8eb7fd71a52c bridge bridge local
751bd423a345 docker_gwbridge bridge local
6ba20168e34f host host local
4e896f9ac4bc none null local
d9652d84d9de ov_net1 overlay global
667cc7ef7427 ov_net2 overlay global
a111191fa67e ov_net3 overlay global原文地址：http://blog.51cto.com/jinlong/2106813
