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docker-networking.md

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Basic Docker Networking Commands

Show networks : docker network ls

Inspect a network : docker network inspect

Create a network : docker network create —driver

Attach a network to container : docker network connect

Detach a network from container : docker network disconnect

By default there are 3 network created :

  • bridge : connects to system network with out security, by default all containers are connected to this network
  • host : connects to system network with out security. Skips virtual networking of docker.
  • none : gives no internet access.

Creating a new network

docker network create my_network This will create a network with default bridge driver configuration.
This can be verified by command docker network inspect my_network , the driver value in json is bridge and the IPAM Config are identical to bridge network.

{
"Name": "my_network",
"Id": "f20c2457b4b01059649e25a3045168c49d43e92320100a5adb09df698f74c104",
"Created": "2020-10-21T18:20:58.717297839Z",
"Scope": "local",
"Driver": "bridge",
"EnableIPv6": false,
"IPAM": {
"Driver": "default",
"Options": {},
"Config": [
{
"Subnet": "172.18.0.0/16",
"Gateway": "172.18.0.1"
}
]
}

To see advanced options which we have can use while creating a network run command docker network create --help

Create a network

Options:

--attachable Enable manual container attachment
--aux-address map Auxiliary IPv4 or IPv6 addresses used by

Network driver (default map[])

--config-from string The network from which copying the configuration
--config-only Create a configuration only network
-d, --driver string Driver to manage the Network (default "bridge")
--gateway strings IPv4 or IPv6 Gateway for the master subnet
--ingress Create swarm routing-mesh network
--internal Restrict external access to the network
--ip-range strings Allocate container ip from a sub-range
--ipam-driver string IP Address Management Driver (default "default")
--ipam-opt map Set IPAM driver specific options (default map[])
--ipv6 Enable IPv6 networking
--label list Set metadata on a network
-o, --opt map Set driver specific options (default map[])
--scope string Control the network's scope
--subnet strings Subnet in CIDR format that represents a
network segment

Running a container with our new network

Assume we want to run a nginx container which is attached to our new network `my_network'

Command docker container run -d --name nginx2 --network my_network nginx. By adding an argument --network we can pass the name of network we want our new container connected to.

This can be verified by inspecting our network my_network docker network inspect my_network, we can see in the container json the name of the continer attached to this network.

"Containers": {
"7b819aa9e8d129b37c549ab9d0657b7347707fbe6d35152121983b8b7b493056": {
"Name": "nginx2",
"EndpointID": "35b117361e396f2154b78f5014558e8efe1e8645b7846d14ab492430dc1e7304",
"MacAddress": "02:42:ac:12:00:02",
"IPv4Address": "172.18.0.2/16",
"IPv6Address": ""
}
}

Connecting/disconnecting a container to an existing network on fly, can be achieved via cli easily.

Command Syntax docker network connect [network_name/hash] [container_name/hash]

Command docker network connect bridge nginx2

In the above command bridge is the network name or we can use the hash that is created automatically by docker, and nginx2 is the container name we ran above. Now when we inspect the container we'll see that our container is now connected to two networks.

 "Networks": {
                "bridge": {
                    "IPAMConfig": {},
                    "Links": null,
                    "Aliases": [],
                    "NetworkID": "310615086fb0946bd2b5a71dcb6a95dc6f68896c9f9666bc814144c0f1be9480",
                    "EndpointID": "e29e7d5045a80b5717a95fed81dc92a161e85b8558a669419391d05a7a251c55",
                    "Gateway": "172.17.0.1",
                    "IPAddress": "172.17.0.2",
                    "IPPrefixLen": 16,
                    "IPv6Gateway": "",
                    "GlobalIPv6Address": "",
                    "GlobalIPv6PrefixLen": 0,
                    "MacAddress": "02:42:ac:11:00:02",
                    "DriverOpts": {}
                },
                "my_network": {
                    "IPAMConfig": null,
                    "Links": null,
                    "Aliases": [
                        "7b819aa9e8d1"
                    ],
                    "NetworkID": "f20c2457b4b01059649e25a3045168c49d43e92320100a5adb09df698f74c104",
                    "EndpointID": "35b117361e396f2154b78f5014558e8efe1e8645b7846d14ab492430dc1e7304",
                    "Gateway": "172.18.0.1",
                    "IPAddress": "172.18.0.2",
                    "IPPrefixLen": 16,
                    "IPv6Gateway": "",
                    "GlobalIPv6Address": "",
                    "GlobalIPv6PrefixLen": 0,
                    "MacAddress": "02:42:ac:12:00:02",
                    "DriverOpts": null
        }
}

Disconnect an image from network

To remove a container from a network we can run command docker network disconnect f20c2457b4b0 nginx2.