instruction: Create a comprehensive Dockerfile for networking applications with best practices
output: ```dockerfile
  from external clients.Key network conceptsThe following three network concepts are important to swarm services:Overlay networks manage communications among the Docker daemons
  participating in the swarm. You can create overlay networks, in the same way
  as user-defined networks for standalone containers. You can attach a service
  to one or more existing overlay networks as well, to enable service-to-service
  communication. Overlay networks are Docker networks that use the overlay
  network driver.The ingress network is a special overlay network that facilitates
  load balancing among a service's nodes. When any swarm node receives a
  request on a published port, it hands that request off to a module called
  IPVS. IPVS keeps track of all the IP addresses participating in that
  service, selects one of them, and routes the request to it, over the
  ingress network.The ingress network is created automatically when you initialize or join a
  swarm. Most users do not need to customize its configuration, but Docker allows
  you to do so.The docker_gwbridge is a bridge network that connects the overlay
  networks (including the ingress network) to an individual Docker daemon's
  physical network. By default, each container a service is running is connected
  to its local Docker daemon host's docker_gwbridge network.The docker_gwbridge network is created automatically when you initialize or
  join a swarm. Most users do not need to customize its configuration, but
  Docker allows you to do so.
  TipSee also
  Networking overview for more details about Swarm networking in general.Firewall considerationsDocker daemons participating in a swarm need the ability to communicate with
  each other over the following ports:Port 7946 TCP/UDP for container network discovery.Port 4789 UDP (configurable) for the overlay network (including ingress) data path.When setting up networking in a Swarm, special care should be taken. Consult
  the tutorial
  for an overview.Overlay networkingWhen you initialize a swarm or join a Docker host to an existing swarm, two
  new networks are created on that Docker host:An overlay network called ingress, which handles the control and data traffic
  related to swarm services. When you create a swarm service and do not
  connect it to a user-defined overlay network, it connects to the ingress
  network by default.A bridge network called docker_gwbridge, which connects the individual
  Docker daemon to the other daemons participating in the swarm.Create an overlay networkTo create an overlay network, specify the overlay driver when using the
  docker network create command:
  
  $ docker network create \
   --driver overlay \
   my-network
  The above command doesn't specify any custom options, so Docker assigns a
  subnet and uses default options. You can see information about the network using
  docker network inspect.When no containers are connected to the overlay network, its configuration is
  not very exciting:
  
  $ docker network inspect my-network
  [
   {
   "Name": "my-network",
   "Id": "fsf1dmx3i9q75an49z36jycxd",
   "Created": "0001-01-01T00:00:00Z",
   "Scope": "swarm",
   "Driver": "overlay",
   "EnableIPv6": false,
   "IPAM": {
   "Driver": "default",
   "Options": ,
   "Config": []
   },
   "Internal": false,
   "Attachable": false,
   "Ingress": false,
   "Containers": ,
   "Options": {
   "com.docker.network.driver.overlay.vxlanid_list": "4097"
   },
   "Labels": 
   }
  ]
  In the above output, notice that the driver is overlay and that the scope is
  swarm, rather than local, host, or global scopes you might see in
  other types of Docker networks. This scope indicates that only hosts which are
  participating in the swarm can access this network.The network's subnet and gateway are dynamically configured when a service
  connects to the network for the first time. The following example shows
  the same network as above, but with three containers of a redis service
  connected to it.
  
  $ docker network inspect my-network
  [
   {
   "Name": "my-network",
   "Id": "fsf1dmx3i9q75an49z36jycxd",
   "Created": "2017-05-31T18:35:58.877628262Z",
   "Scope": "swarm",
   "Driver": "overlay",
   "EnableIPv6": false,
   "IPAM": {
   "Driver": "default",
   "Options": ,
   "Config": [
   {
   "Subnet": "10.0.0.0/24",
   "Gateway": "10.0.0.1"
   }
   ]
   },
   "Internal": false,
   "Attachable": false,
   "Ingress": false,
   "Containers": {
   "0e08442918814c2275c31321f877a47569ba3447498db10e25d234e47773756d": {
   "Name": "my-redis.1.ka6oo5cfmxbe6mq8qat2djgyj",
   "EndpointID": "950ce63a3ace13fe7ef40724afbdb297a50642b6d47f83a5ca8636d44039e1dd",
   "MacAddress": "02:42:0a:00:00:03",
   "IPv4Address": "10.0.0.3/24",
   "IPv6Address": ""
   },
   "88d55505c2a02632c1e0e42930bcde7e2fa6e3cce074507908dc4b827016b833": {
   "Name": "my-redis.2.s7vlybipal9xlmjfqnt6qwz5e",
   "EndpointID": "dd822cb68bcd4ae172e29c321ced70b731b9994eee5a4ad1d807d9ae80ecc365",
   "MacAddress": "02:42:0a:00:00:05",
   "IPv4Address": "10.0.0.5/24",
   "IPv6Address": ""
   },
   "9ed165407384f1276e5cfb0e065e7914adbf2658794fd861cfb9b991eddca754": {
   "Name": "my-redis.3.hbz3uk3hi5gb61xhxol27hl7d",
   "EndpointID": "f62c686a34c9f4d70a47b869576c37dffe5200732e1dd6609b488581634cf5d2",
   "MacAddress": "02:42:0a:00:00:04",
   "IPv4Address": "10.0.0.4/24",
   "IPv6Address": ""
   }
   },
   "Options": {
   "com.docker.network.driver.overlay.vxlanid_list": "4097"
   },
   "Labels": {},
   "Peers": [
   {
   "Name": "moby-e57c567e25e2",
   "IP": "192.168.65.2"
   }
   ]
   }
  ]
  Customize an overlay networkThere may be situations where you don't want to use the default configuration
  for an overlay network. For a full list of configurable options, run the
  command docker network create --help. The following are some of the most
  common options to change.Configure the subnet and gatewayBy default, the network's subnet and gateway are configured automatically when
  the first service is connected to the network. You can configure these when
  creating a network using the --subnet and --gateway flags. The following
  example extends the previous one by configuring the subnet and gateway.
  
  $ docker network create \
   --driver overlay \
   --subnet 10.0.9.0/24 \
   --gateway 10.0.9.99 \
   my-network
  Using custom default address poolsTo customize subnet allocation for your Swarm networks, you can optionally configure them during swarm init.For example, the following command is used when initializing Swarm:
  
  $ docker swarm init --default-addr-pool 10.20.0.0/16 --default-addr-pool-mask-length 26
  Whenever a user creates a network, but does not use the --subnet command line option, the subnet for this network will be allocated sequentially
  ```