A brief discussion on the preliminary practice of Docker container interconnection

1. Interconnection between Docker containers

Docker has now become a lightweight virtualization solution. On the same host machine, all containers can be interconnected through bridges. If you have experience with Docker before, you may be used to using --link to interconnect containers. As Docker gradually improves, it is strongly recommended that you use a bridge to interconnect containers.

2. Practice process

1. Create a network my-net:

[root@ChatDevOps ~]# docker network create my-net
71b42506de62797889372ea4a5270f905f79a19cf80e308119c02e529b89c94e
[root@ChatDevOps ~]# docker network ls
NETWORK ID NAME DRIVER SCOPE
3dec5cbb852e bridge bridge local
6dd6dcfc2f26 host host local
71b42506de62 my-net bridge local
4c142a02cd6b none null local

2. Specify the bridge network when creating the docker container:

[root@ChatDevOps docker]# docker create -it --name d1 --network my-net -p 8080:80 ubuntu:14.04
4776b65db566f370cad5da3a9354a12c7e4f9badab53647b7e30e1e8f343ae3d
[root@ChatDevOps docker]# docker start d1
d1

In this command, docker create can also be used as docker container create, and the two are equivalent. –name specifies the name of the container, –network specifies the network name of the container, the bridge mode defaults to bridge, and -p or –publish specifies the mapped port. If the network specified in this step has not been created in advance, the container will not be able to start normally. At this point, you can create a network for the container and start the container again.

3. You can also specify an already created network when running a docker container:

[root@ChatDevOps docker]# docker run -it --name d2 --network my-net --publish 8081:80 ubuntu:14.04 /bin/bash
root@07fd516911d0:/# ping d1
PING d1 (172.18.0.2) 56(84) bytes of data.
64 bytes from d1.my-net (172.18.0.2): icmp_seq=1 ttl=64 time=0.115 ms
root@4776b65db566:/# ping d2
PING d2 (172.18.0.3) 56(84) bytes of data.
64 bytes from d2.my-net (172.18.0.3): icmp_seq=1 ttl=64 time=0.062 ms

You can ping containers on the same bridge using the container name. You can also ping its IP directly.

Conclusion

1. After the docker installation is complete, the docker container has three networks, as follows:

[root@ChatDevOps ~]# docker network ls
NETWORK ID NAME DRIVER SCOPE
3dec5cbb852e bridge bridge local
6dd6dcfc2f26 host host local
4c142a02cd6b none null local

2. All container networks in the same network are interoperable.

3. The DNS configuration in the container's network configuration can be configured in the /etc/docker/daemon.json file on the host, referring to the official format:

{
 "bip": "192.168.1.5/24",
 "fixed-cidr": "192.168.1.5/25",
 "fixed-cidr-v6": "2001:db8::/64",
 "mtu": 1500,
 "default-gateway": "10.20.1.1",
 "default-gateway-v6": "2001:db8:abcd::89",
 "dns": ["10.20.1.2","10.20.1.3"]
}

You can configure it according to the actual situation.

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