21 Days of Docker-Day 10- Docker Networking – Part 2

Welcome to Day 10 of 21 Days of Docker. On Day 9, I discussed the basics of Docker Networking and we use the default bridge network.

21 Days of Docker-Day 9- Docker Networking – Part 1

• Let’s take one step further and now move to User-defined bridge networks are superior to the default bridge network.

• To create a user-defined bridge

$ docker network create my-network
42ed6f1adc7a9b4ec687e99a1cbbdde8a1a3d1f86bef5e5376e121b29c8f760b

• To verify the bridge network

$ docker network ls
NETWORK ID          NAME                DRIVER              SCOPE
45decc7a84de        bridge              bridge              local
18ab553b68ea        host                host                local
42ed6f1adc7a        my-network          bridge              local
b49ee4b5f50f        none                null                local

• To get detailed info about the network we just created

$ docker network inspect my-network
[
    {
        "Name": "my-network",
        "Id": "42ed6f1adc7a9b4ec687e99a1cbbdde8a1a3d1f86bef5e5376e121b29c8f760b",
        "Created": "2019-10-15T22:24:36.801033922Z",
        "Scope": "local",
        "Driver": "bridge",
        "EnableIPv6": false,
        "IPAM": {
            "Driver": "default",
            "Options": {},
            "Config": [
                {
                    "Subnet": "172.18.0.0/16",
                    "Gateway": "172.18.0.1"
                }
            ]
        },
        "Internal": false,
        "Attachable": false,
        "Ingress": false,
        "ConfigFrom": {
            "Network": ""
        },
        "ConfigOnly": false,
        "Containers": {},
        "Options": {},
        "Labels": {}
    }
]

Connect a container to a user-defined bridge

• When we create a new container, you can specify one or more --network flags

$ docker container run --name mycustomnetcontainer --network my-network -dt centos bash
a7b364c933b636bd1e0b454fcc7d1ab810dc60105716e1a0e1984a50486a6c20

• If we run the network inspect again

$ docker network inspect my-network
[
    {
        "Name": "my-network",
        "Id": "42ed6f1adc7a9b4ec687e99a1cbbdde8a1a3d1f86bef5e5376e121b29c8f760b",
        "Created": "2019-10-15T22:24:36.801033922Z",
        "Scope": "local",
        "Driver": "bridge",
        "EnableIPv6": false,
        "IPAM": {
            "Driver": "default",
            "Options": {},
            "Config": [
                {
                    "Subnet": "172.18.0.0/16",
                    "Gateway": "172.18.0.1"
                }
            ]
        },
        "Internal": false,
        "Attachable": false,
        "Ingress": false,
        "ConfigFrom": {
            "Network": ""
        },
        "ConfigOnly": false,
        "Containers": {
            "a7b364c933b636bd1e0b454fcc7d1ab810dc60105716e1a0e1984a50486a6c20": {
                "Name": "mycustomnetcontainer", <--------------------------------
                "EndpointID": "5e0fe7027848591ce9c2305c2428b3a67f45f143976811f4419c2600f04fe63e",
                "MacAddress": "02:42:ac:12:00:02",
                "IPv4Address": "172.18.0.2/16",
                "IPv6Address": ""
            }
        },
        "Options": {},
        "Labels": {}
    }
]

• If we want we can connect any existing network container on the fly to this network

$ docker network connect my-network mycentosnewcont

• If we run docker inspect again, you will see one more container

$ docker network inspect my-network
[
    {
        "Name": "my-network",
        "Id": "42ed6f1adc7a9b4ec687e99a1cbbdde8a1a3d1f86bef5e5376e121b29c8f760b",
        "Created": "2019-10-15T22:24:36.801033922Z",
        "Scope": "local",
        "Driver": "bridge",
        "EnableIPv6": false,
        "IPAM": {
            "Driver": "default",
            "Options": {},
            "Config": [
                {
                    "Subnet": "172.18.0.0/16",
                    "Gateway": "172.18.0.1"
                }
            ]
        },
        "Internal": false,
        "Attachable": false,
        "Ingress": false,
        "ConfigFrom": {
            "Network": ""
        },
        "ConfigOnly": false,
        "Containers": {
            "402332f2de72b214077b6312bef8b891a6564fae0f2e386032fb0abff736b29c": {
                "Name": "mycentosnewcont",<------
                "EndpointID": "312d1d7fa00c5e638a5b7b23ee0734b01571df3601be64711288ebfad1b3d23d",
                "MacAddress": "02:42:ac:12:00:03",
                "IPv4Address": "172.18.0.3/16",
                "IPv6Address": ""
            },
            "a7b364c933b636bd1e0b454fcc7d1ab810dc60105716e1a0e1984a50486a6c20": {
                "Name": "mycustomnetcontainer",
                "EndpointID": "5e0fe7027848591ce9c2305c2428b3a67f45f143976811f4419c2600f04fe63e",
                "MacAddress": "02:42:ac:12:00:02",
                "IPv4Address": "172.18.0.2/16",
                "IPv6Address": ""
            }
        },
        "Options": {},
        "Labels": {}
    }
]