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DockerCLI/docs/reference/commandline/network_create.md

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network create

Create a network

Options

Name Type Default Description
--attachable Enable manual container attachment
--aux-address map map[] Auxiliary IPv4 or IPv6 addresses used by Network driver
--config-from string The network from which to copy the configuration
--config-only Create a configuration only network
-d, --driver string bridge Driver to manage the Network
--gateway stringSlice IPv4 or IPv6 Gateway for the master subnet
--ingress Create swarm routing-mesh network
--internal Restrict external access to the network
--ip-range stringSlice Allocate container ip from a sub-range
--ipam-driver string default IP Address Management Driver
--ipam-opt map map[] Set IPAM driver specific options
--ipv6 Enable IPv6 networking
--label list Set metadata on a network
-o, --opt map map[] Set driver specific options
--scope string Control the network's scope
--subnet stringSlice Subnet in CIDR format that represents a network segment

Description

Creates a new network. The DRIVER accepts bridge or overlay which are the built-in network drivers. If you have installed a third party or your own custom network driver you can specify that DRIVER here also. If you don't specify the --driver option, the command automatically creates a bridge network for you. When you install Docker Engine it creates a bridge network automatically. This network corresponds to the docker0 bridge that Docker Engine has traditionally relied on. When you launch a new container with docker run it automatically connects to this bridge network. You cannot remove this default bridge network, but you can create new ones using the network create command.

$ docker network create -d bridge my-bridge-network

Bridge networks are isolated networks on a single Docker Engine installation. If you want to create a network that spans multiple Docker hosts each running Docker Engine, you must enable Swarm mode, and create an overlay network. To read more about overlay networks with Swarm mode, see "use overlay networks".

Once you have enabled swarm mode, you can create a swarm-scoped overlay network:

$ docker network create --scope=swarm --attachable -d overlay my-multihost-network

By default, swarm-scoped networks do not allow manually started containers to be attached. This restriction is added to prevent someone that has access to a non-manager node in the swarm cluster from running a container that is able to access the network stack of a swarm service.

The --attachable option used in the example above disables this restriction, and allows for both swarm services and manually started containers to attach to the overlay network.

Network names must be unique. The Docker daemon attempts to identify naming conflicts but this is not guaranteed. It is the user's responsibility to avoid name conflicts.

Overlay network limitations

You should create overlay networks with /24 blocks (the default), which limits you to 256 IP addresses, when you create networks using the default VIP-based endpoint-mode. This recommendation addresses limitations with swarm mode. If you need more than 256 IP addresses, do not increase the IP block size. You can either use dnsrr endpoint mode with an external load balancer, or use multiple smaller overlay networks. See Configure service discovery for more information about different endpoint modes.

Examples

Connect containers

When you start a container, use the --network flag to connect it to a network. This example adds the busybox container to the mynet network:

$ docker run -itd --network=mynet busybox

If you want to add a container to a network after the container is already running, use the docker network connect subcommand.

You can connect multiple containers to the same network. Once connected, the containers can communicate using only another container's IP address or name. For overlay networks or custom plugins that support multi-host connectivity, containers connected to the same multi-host network but launched from different daemons can also communicate in this way.

You can disconnect a container from a network using the docker network disconnect command.

Specify advanced options

When you create a network, Docker Engine creates a non-overlapping subnetwork for the network by default. This subnetwork is not a subdivision of an existing network. It is purely for ip-addressing purposes. You can override this default and specify subnetwork values directly using the --subnet option. On a bridge network you can only create a single subnet:

$ docker network create --driver=bridge --subnet=192.168.0.0/16 br0

Additionally, you also specify the --gateway --ip-range and --aux-address options.

$ docker network create \
  --driver=bridge \
  --subnet=172.28.0.0/16 \
  --ip-range=172.28.5.0/24 \
  --gateway=172.28.5.254 \
  br0

If you omit the --gateway flag, Docker Engine selects one for you from inside a preferred pool. For overlay networks and for network driver plugins that support it you can create multiple subnetworks. This example uses two /25 subnet mask to adhere to the current guidance of not having more than 256 IPs in a single overlay network. Each of the subnetworks has 126 usable addresses.

$ docker network create -d overlay \
  --subnet=192.168.10.0/25 \
  --subnet=192.168.20.0/25 \
  --gateway=192.168.10.100 \
  --gateway=192.168.20.100 \
  --aux-address="my-router=192.168.10.5" --aux-address="my-switch=192.168.10.6" \
  --aux-address="my-printer=192.168.20.5" --aux-address="my-nas=192.168.20.6" \
  my-multihost-network

Be sure that your subnetworks do not overlap. If they do, the network create fails and Docker Engine returns an error.

Bridge driver options

When creating a custom network, the default network driver (i.e. bridge) has additional options that can be passed. The following are those options and the equivalent Docker daemon flags used for docker0 bridge:

Option Equivalent Description
com.docker.network.bridge.name - Bridge name to be used when creating the Linux bridge
com.docker.network.bridge.enable_ip_masquerade --ip-masq Enable IP masquerading
com.docker.network.bridge.enable_icc --icc Enable or Disable Inter Container Connectivity
com.docker.network.bridge.host_binding_ipv4 --ip Default IP when binding container ports
com.docker.network.driver.mtu --mtu Set the containers network MTU
com.docker.network.container_iface_prefix - Set a custom prefix for container interfaces

The following arguments can be passed to docker network create for any network driver, again with their approximate equivalents to Docker daemon flags used for the docker0 bridge:

Argument Equivalent Description
--gateway - IPv4 or IPv6 Gateway for the master subnet
--ip-range --fixed-cidr Allocate IPs from a range
--internal - Restrict external access to the network
--ipv6 --ipv6 Enable IPv6 networking
--subnet --bip Subnet for network

For example, let's use -o or --opt options to specify an IP address binding when publishing ports:

$ docker network create \
    -o "com.docker.network.bridge.host_binding_ipv4"="172.19.0.1" \
    simple-network

Network internal mode (--internal)

Containers on an internal network may communicate between each other, but not with any other network, as no default route is configured and firewall rules are set up to drop all traffic to or from other networks. Communication with the gateway IP address (and thus appropriately configured host services) is possible, and the host may communicate with any container IP directly.

By default, when you connect a container to an overlay network, Docker also connects a bridge network to it to provide external connectivity. If you want to create an externally isolated overlay network, you can specify the --internal option.

Network ingress mode (--ingress)

You can create the network which will be used to provide the routing-mesh in the swarm cluster. You do so by specifying --ingress when creating the network. Only one ingress network can be created at the time. The network can be removed only if no services depend on it. Any option available when creating an overlay network is also available when creating the ingress network, besides the --attachable option.

$ docker network create -d overlay \
  --subnet=10.11.0.0/16 \
  --ingress \
  --opt com.docker.network.driver.mtu=9216 \
  --opt encrypted=true \
  my-ingress-network

Run services on predefined networks

You can create services on the predefined Docker networks bridge and host.

$ docker service create --name my-service \
  --network host \
  --replicas 2 \
  busybox top

Swarm networks with local scope drivers

You can create a swarm network with local scope network drivers. You do so by promoting the network scope to swarm during the creation of the network. You will then be able to use this network when creating services.

$ docker network create -d bridge \
  --scope swarm \
  --attachable \
  swarm-network

For network drivers which provide connectivity across hosts (ex. macvlan), if node specific configurations are needed in order to plumb the network on each host, you will supply that configuration via a configuration only network. When you create the swarm scoped network, you will then specify the name of the network which contains the configuration.

node1$ docker network create --config-only --subnet 192.168.100.0/24 --gateway 192.168.100.115 mv-config
node2$ docker network create --config-only --subnet 192.168.200.0/24 --gateway 192.168.200.202 mv-config
node1$ docker network create -d macvlan --scope swarm --config-from mv-config --attachable swarm-network

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