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allencloud d0081a0f47 better command docker network create -h output

Signed-off-by: allencloud <allen.sun@daocloud.io>

2016-07-16 15:32:17 +08:00

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network create

Usage:	docker network create [OPTIONS]

Create a network

Options:
      --aux-address value    Auxiliary IPv4 or IPv6 addresses used by Network
                             driver (default map[])
  -d, --driver string        Driver to manage the Network (default "bridge")
      --gateway value        IPv4 or IPv6 Gateway for the master subnet (default [])
      --help                 Print usage
      --internal             Restrict external access to the network
      --ip-range value       Allocate container ip from a sub-range (default [])
      --ipam-driver string   IP Address Management Driver (default "default")
      --ipam-opt value       Set IPAM driver specific options (default map[])
      --ipv6                 Enable IPv6 networking
      --label value          Set metadata on a network (default [])
  -o, --opt value            Set driver specific options (default map[])
      --subnet value         Subnet in CIDR format that represents a
                             network segment (default [])

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 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 Engine installation. If you want to create a network that spans multiple Docker hosts each running an Engine, you must create an overlay network. Unlike bridge networks, overlay networks require some pre-existing conditions before you can create one. These conditions are:

Access to a key-value store. Engine supports Consul, Etcd, and ZooKeeper (Distributed store) key-value stores.
A cluster of hosts with connectivity to the key-value store.
A properly configured Engine daemon on each host in the cluster.

The dockerd options that support the overlay network are:

--cluster-store
--cluster-store-opt
--cluster-advertise

To read more about these options and how to configure them, see "Get started with multi-host network".

While not required, it is a good idea to install Docker Swarm to manage the cluster that makes up your network. Swarm provides sophisticated discovery and server management tools that can assist your implementation.

Once you have prepared the overlay network prerequisites you simply choose a Docker host in the cluster and issue the following to create the network:

$ docker network create -d overlay my-multihost-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.

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 Engines can also communicate in this way.

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

Specifying advanced options

When you create a network, 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 the 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.

$ docker network create -d overlay \
  --subnet=192.168.0.0/16 \
  --subnet=192.170.0.0/16 \
  --gateway=192.168.0.100 \ 
  --gateway=192.170.0.100 \
  --ip-range=192.168.1.0/24 \
  --aux-address a=192.168.1.5 --aux-address b=192.168.1.6 \
  --aux-address a=192.170.1.5 --aux-address b=192.170.1.6 \
  my-multihost-network

Be sure that your subnetworks do not overlap. If they do, the network create fails and 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.mtu`	`--mtu`	Set the containers network MTU

The following arguments can be passed to docker network create for any network driver, again with their approximate equivalents to docker daemon.

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

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.

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