In this lab you will learn about key Docker Networking concepts. You will get your hands dirty by going through examples of a few basic networking concepts, learn about Bridge networking, and finally Overlay networking.

Difficulty: Beginner to Intermediate

Time: Approximately 45 minutes

Tasks:

Section #1 - Networking Basics

Step 1: The Docker Network Command

The docker network command is the main command for configuring and managing container networks. Run the docker network command from the first terminal.

docker network

Usage:	docker network COMMAND

Manage networks

Options:
      --help   Print usage

Commands:
  connect     Connect a container to a network
  create      Create a network
  disconnect  Disconnect a container from a network
  inspect     Display detailed information on one or more networks
  ls          List networks
  prune       Remove all unused networks
  rm          Remove one or more networks

Run 'docker network COMMAND --help' for more information on a command.

The command output shows how to use the command as well as all of the docker network sub-commands. As you can see from the output, the docker network command allows you to create new networks, list existing networks, inspect networks, and remove networks. It also allows you to connect and disconnect containers from networks.

Step 2: List networks

Run a docker network ls command to view existing container networks on the current Docker host.

docker network ls
NETWORK ID          NAME                DRIVER              SCOPE
3430ad6f20bf        bridge              bridge              local
a7449465c379        host                host                local
06c349b9cc77        none                null                local

The output above shows the container networks that are created as part of a standard installation of Docker.

New networks that you create will also show up in the output of the docker network ls command.

You can see that each network gets a unique ID and NAME. Each network is also associated with a single driver. Notice that the “bridge” network and the “host” network have the same name as their respective drivers.

Step 3: Inspect a network

The docker network inspect command is used to view network configuration details. These details include; name, ID, driver, IPAM driver, subnet info, connected containers, and more.

Use docker network inspect <network> to view configuration details of the container networks on your Docker host. The command below shows the details of the network called bridge.

docker network inspect bridge
[
    {
        "Name": "bridge",
        "Id": "3430ad6f20bf1486df2e5f64ddc93cc4ff95d81f59b6baea8a510ad500df2e57",
        "Created": "2017-04-03T16:49:58.6536278Z",
        "Scope": "local",
        "Driver": "bridge",
        "EnableIPv6": false,
        "IPAM": {
            "Driver": "default",
            "Options": null,
            "Config": [
                {
                    "Subnet": "172.17.0.0/16",
                    "Gateway": "172.17.0.1"
                }
            ]
        },
        "Internal": false,
        "Attachable": false,
        "Containers": {},
        "Options": {
            "com.docker.network.bridge.default_bridge": "true",
            "com.docker.network.bridge.enable_icc": "true",
            "com.docker.network.bridge.enable_ip_masquerade": "true",
            "com.docker.network.bridge.host_binding_ipv4": "0.0.0.0",
            "com.docker.network.bridge.name": "docker0",
            "com.docker.network.driver.mtu": "1500"
        },
        "Labels": {}
    }
]

NOTE: The syntax of the docker network inspect command is docker network inspect <network>, where <network> can be either network name or network ID. In the example above we are showing the configuration details for the network called “bridge”. Do not confuse this with the “bridge” driver.

Step 4: List network driver plugins

The docker info command shows a lot of interesting information about a Docker installation.

Run the docker info command and locate the list of network plugins.

docker info
Containers: 0
 Running: 0
 Paused: 0
 Stopped: 0
Images: 0
Server Version: 17.03.1-ee-3
Storage Driver: aufs
<Snip>
Plugins:
 Volume: local
 Network: bridge host macvlan null overlay
Swarm: inactive
Runtimes: runc
<Snip>

The output above shows the bridge, host,macvlan, null, and overlay drivers.

Section #2 - Bridge Networking

Step 1: The Basics

Every clean installation of Docker comes with a pre-built network called bridge. Verify this with the docker network ls.

docker network ls
NETWORK ID          NAME                DRIVER              SCOPE
3430ad6f20bf        bridge              bridge              local
a7449465c379        host                host                local
06c349b9cc77        none                null                local

The output above shows that the bridge network is associated with the bridge driver. It’s important to note that the network and the driver are connected, but they are not the same. In this example the network and the driver have the same name - but they are not the same thing!

The output above also shows that the bridge network is scoped locally. This means that the network only exists on this Docker host. This is true of all networks using the bridge driver - the bridge driver provides single-host networking.

All networks created with the bridge driver are based on a Linux bridge (a.k.a. a virtual switch).

Install the brctl command and use it to list the Linux bridges on your Docker host. You can do this by running sudo apt-get install bridge-utils.

apk update
apk add bridge

Then, list the bridges on your Docker host, by running brctl show.

brctl show
bridge name	bridge id		STP enabled	interfaces
docker0		8000.024252ed52f7	no

The output above shows a single Linux bridge called docker0. This is the bridge that was automatically created for the bridge network. You can see that it has no interfaces currently connected to it.

You can also use the ip a command to view details of the docker0 bridge.

ip a
<Snip>
3: docker0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN group default
    link/ether 02:42:52:ed:52:f7 brd ff:ff:ff:ff:ff:ff
    inet 172.17.0.1/16 scope global docker0
       valid_lft forever preferred_lft forever

Step 2: Connect a container

The bridge network is the default network for new containers. This means that unless you specify a different network, all new containers will be connected to the bridge network.

Create a new container by running docker run -dt ubuntu sleep infinity.

docker run -dt ubuntu sleep infinity
Unable to find image 'ubuntu:latest' locally
latest: Pulling from library/ubuntu
d54efb8db41d: Pull complete
f8b845f45a87: Pull complete
e8db7bf7c39f: Pull complete
9654c40e9079: Pull complete
6d9ef359eaaa: Pull complete
Digest: sha256:dd7808d8792c9841d0b460122f1acf0a2dd1f56404f8d1e56298048885e45535
Status: Downloaded newer image for ubuntu:latest
846af8479944d406843c90a39cba68373c619d1feaa932719260a5f5afddbf71

This command will create a new container based on the ubuntu:latest image and will run the sleep command to keep the container running in the background. You can verify our example container is up by running docker ps.

docker ps
CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS               NAMES
846af8479944        ubuntu              "sleep infinity"    55 seconds ago      Up 54 seconds                           heuristic_boyd

As no network was specified on the docker run command, the container will be added to the bridge network.

Run the brctl show command again.

brctl show
bridge name	bridge id		STP enabled	interfaces
docker0		8000.024252ed52f7	no		vethd630437

Notice how the docker0 bridge now has an interface connected. This interface connects the docker0 bridge to the new container just created.

You can inspect the bridge network again, by running docker network inspect bridge, to see the new container attached to it.

docker network inspect bridge
<Snip>
        "Containers": {
            "846af8479944d406843c90a39cba68373c619d1feaa932719260a5f5afddbf71": {
                "Name": "heuristic_boyd",
                "EndpointID": "1265c418f0b812004d80336bafdc4437eda976f166c11dbcc97d365b2bfa91e5",
                "MacAddress": "02:42:ac:11:00:02",
                "IPv4Address": "172.17.0.2/16",
                "IPv6Address": ""
            }
        },
<Snip>

Step 3: Test network connectivity

The output to the previous docker network inspect command shows the IP address of the new container. In the previous example it is “172.17.0.2” but yours might be different.

Ping the IP address of the container from the shell prompt of your Docker host by running ping -c5 <IPv4 Address>. Remember to use the IP of the container in your environment.

ping -c5 172.17.0.2
PING 172.17.0.2 (172.17.0.2) 56(84) bytes of data.
64 bytes from 172.17.0.2: icmp_seq=1 ttl=64 time=0.055 ms
64 bytes from 172.17.0.2: icmp_seq=2 ttl=64 time=0.031 ms
64 bytes from 172.17.0.2: icmp_seq=3 ttl=64 time=0.034 ms
64 bytes from 172.17.0.2: icmp_seq=4 ttl=64 time=0.041 ms
64 bytes from 172.17.0.2: icmp_seq=5 ttl=64 time=0.047 ms

--- 172.17.0.2 ping statistics ---
5 packets transmitted, 5 received, 0% packet loss, time 4075ms
rtt min/avg/max/mdev = 0.031/0.041/0.055/0.011 ms

The replies above show that the Docker host can ping the container over the bridge network. But, we can also verify the container can connect to the outside world too. Lets log into the container, install the ping program, and then ping www.github.com.

First, we need to get the ID of the container started in the previous step. You can run docker ps to get that.

docker ps
CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS               NAMES
846af8479944        ubuntu              "sleep infinity"    7 minutes ago       Up 7 minutes                            heuristic_boyd

Next, lets run a shell inside that ubuntu container, by running docker exec -it <CONTAINER ID> /bin/bash.

docker exec -it yourcontainerid /bin/bash
root@846af8479944:/#

Next, we need to install the ping program. So, lets run apt-get update && apt-get install -y iputils-ping.

apt-get update && apt-get install -y iputils-ping

Lets ping www.github.com by running ping -c5 www.github.com

  ping -c5 www.github.com
PING www.docker.com (104.239.220.248) 56(84) bytes of data.
64 bytes from 104.239.220.248: icmp_seq=1 ttl=45 time=38.1 ms
64 bytes from 104.239.220.248: icmp_seq=2 ttl=45 time=37.3 ms
64 bytes from 104.239.220.248: icmp_seq=3 ttl=45 time=37.5 ms
64 bytes from 104.239.220.248: icmp_seq=4 ttl=45 time=37.5 ms
64 bytes from 104.239.220.248: icmp_seq=5 ttl=45 time=37.5 ms

--- www.docker.com ping statistics ---
5 packets transmitted, 5 received, 0% packet loss, time 4003ms
rtt min/avg/max/mdev = 37.372/37.641/38.143/0.314 ms

Finally, lets disconnect our shell from the container, by running exit.

exit

We should also stop this container so we clean things up from this test, by running docker stop <CONTAINER ID>.

docker stop yourcontainerid

This shows that the new container can ping the internet and therefore has a valid and working network configuration.

Step 4: Configure NAT for external connectivity

In this step we’ll start a new NGINX container and map port 8080 on the Docker host to port 80 inside of the container. This means that traffic that hits the Docker host on port 8080 will be passed on to port 80 inside the container.

NOTE: If you start a new container from the official NGINX image without specifying a command to run, the container will run a basic web server on port 80.

Start a new container based off the official NGINX image by running docker run --name web1 -d -p 8080:80 nginx.

docker run --name web1 -d -p 8080:80 nginx
Unable to find image 'nginx:latest' locally
latest: Pulling from library/nginx
6d827a3ef358: Pull complete
b556b18c7952: Pull complete
03558b976e24: Pull complete
9abee7e1ef9d: Pull complete
Digest: sha256:52f84ace6ea43f2f58937e5f9fc562e99ad6876e82b99d171916c1ece587c188
Status: Downloaded newer image for nginx:latest
4e0da45b0f169f18b0e1ee9bf779500cb0f756402c0a0821d55565f162741b3e

Review the container status and port mappings by running docker ps.

docker ps
CONTAINER ID        IMAGE               COMMAND                  CREATED             STATUS              PORTS                           NAMES
4e0da45b0f16        nginx               "nginx -g 'daemon ..."   2 minutes ago       Up 2 minutes        443/tcp, 0.0.0.0:8080->80/tcp   web1

The top line shows the new web1 container running NGINX. Take note of the command the container is running as well as the port mapping - 0.0.0.0:8080->80/tcp maps port 8080 on all host interfaces to port 80 inside the web1 container. This port mapping is what effectively makes the containers web service accessible from external sources (via the Docker hosts IP address on port 8080).

Now that the container is running and mapped to a port on a host interface you can test connectivity to the NGINX web server.

To complete the following task you will need the IP address of your Docker host. This will need to be an IP address that you can reach (e.g. your lab is hosted in Azure so this will be the instance’s Public IP - the one you SSH’d into). Just point your web browser to the IP and port 8080 of your Docker host. Also, if you try connecting to the same IP address on a different port number it will fail.

If for some reason you cannot open a session from a web broswer, you can connect from your Docker host using the curl 127.0.0.1:8080 command.

curl 127.0.0.1:8080
<!DOCTYPE html>
<html>
<Snip>
<head>
<title>Welcome to nginx!</title>
    <Snip>
<p><em>Thank you for using nginx.</em></p>
</body>
</html>

If you try and curl the IP address on a different port number it will fail.

NOTE: The port mapping is actually port address translation (PAT).

Section #3 - Overlay Networking

Step 1: The Basics

In this step you’ll initialize a new Swarm, join a single worker node, and verify the operations worked.

Run docker swarm init --advertise-addr $(hostname -i).

docker swarm init --advertise-addr $(hostname -i)
Swarm initialized: current node (rzyy572arjko2w0j82zvjkc6u) is now a manager.

To add a worker to this swarm, run the following command:

    docker swarm join \
    --token SWMTKN-1-69b2x1u2wtjdmot0oqxjw1r2d27f0lbmhfxhvj83chln1l6es5-37ykdpul0vylenefe2439cqpf \
    10.0.0.5:2377

To add a manager to this swarm, run 'docker swarm join-token manager' and follow the instructions.

In the first terminal copy the entire docker swarm join ... command that is displayed as part of the output from your terminal output. Then, paste the copied command into the second terminal.

docker swarm join \
>     --token SWMTKN-1-69b2x1u2wtjdmot0oqxjw1r2d27f0lbmhfxhvj83chln1l6es5-37ykdpul0vylenefe2439cqpf \
>     10.0.0.5:2377
This node joined a swarm as a worker.

Run a docker node ls to verify that both nodes are part of the Swarm.

docker node ls
ID                           HOSTNAME  STATUS  AVAILABILITY  MANAGER STATUS
ijjmqthkdya65h9rjzyngdn48    node2   Ready   Active
rzyy572arjko2w0j82zvjkc6u *  node1   Ready   Active        Leader

The ID and HOSTNAME values may be different in your lab. The important thing to check is that both nodes have joined the Swarm and are ready and active.

Step 2: Create an overlay network

Now that you have a Swarm initialized it’s time to create an overlay network.

Create a new overlay network called “overnet” by running docker network create -d overlay overnet.

docker network create -d overlay overnet
wlqnvajmmzskn84bqbdi1ytuy

Use the docker network ls command to verify the network was created successfully.

docker network ls
NETWORK ID          NAME                DRIVER              SCOPE
3430ad6f20bf        bridge              bridge              local
a4d584350f09        docker_gwbridge     bridge              local
a7449465c379        host                host                local
8hq1n8nak54x        ingress             overlay             swarm
06c349b9cc77        none                null                local
wlqnvajmmzsk        overnet             overlay             swarm

The new “overnet” network is shown on the last line of the output above. Notice how it is associated with the overlay driver and is scoped to the entire Swarm.

NOTE: The other new networks (ingress and docker_gwbridge) were created automatically when the Swarm cluster was created.

Run the same docker network ls command from the second terminal.

docker network ls
NETWORK ID          NAME                DRIVER              SCOPE
55f10b3fb8ed        bridge              bridge              local
b7b30433a639        docker_gwbridge     bridge              local
a7449465c379        host                host                local
8hq1n8nak54x        ingress             overlay             swarm
06c349b9cc77        none                null                local

Notice that the “overnet” network does not appear in the list. This is because Docker only extends overlay networks to hosts when they are needed. This is usually when a host runs a task from a service that is created on the network. We will see this shortly.

Use the docker network inspect <network> command to view more detailed information about the “overnet” network. You will need to run this command from the first terminal.

docker network inspect overnet
[
    {
        "Name": "overnet",
        "Id": "wlqnvajmmzskn84bqbdi1ytuy",
        "Created": "0001-01-01T00:00:00Z",
        "Scope": "swarm",
        "Driver": "overlay",
        "EnableIPv6": false,
        "IPAM": {
            "Driver": "default",
            "Options": null,
            "Config": []
        },
        "Internal": false,
        "Attachable": false,
        "Containers": null,
        "Options": {
            "com.docker.network.driver.overlay.vxlanid_list": "4097"
        },
        "Labels": null
    }
]

Step 3: Create a service

Now that we have a Swarm initialized and an overlay network, it’s time to create a service that uses the network.

Execute the following command from the first terminal to create a new service called myservice on the overnet network with two tasks/replicas.

docker service create --name myservice \
--network overnet \
--replicas 2 \
ubuntu sleep infinity
ov30itv6t2n7axy2goqbfqt5e

Verify that the service is created and both replicas are up by running docker service ls.

docker service ls
ID            NAME       MODE        REPLICAS  IMAGE
ov30itv6t2n7  myservice  replicated  2/2       ubuntu:latest

The 2/2 in the REPLICAS column shows that both tasks in the service are up and running.

Verify that a single task (replica) is running on each of the two nodes in the Swarm by running docker service ps myservice.

docker service ps myservice
ID            NAME         IMAGE          NODE     DESIRED STATE  CURRENT STATE               ERROR  PORTS
riicggj5tuta  myservice.1  ubuntu:latest  node2  Running        Running about a minute ago
nlozn82wsttv  myservice.2  ubuntu:latest  node1  Running        Running about a minute ago

The ID and NODE values might be different in your output. The important thing to note is that each task/replica is running on a different node.

Now that the second node is running a task on the “overnet” network it will be able to see the “overnet” network. Lets run docker network ls from the second terminal to verify this.

docker network ls
NETWORK ID          NAME                DRIVER              SCOPE
55f10b3fb8ed        bridge              bridge              local
b7b30433a639        docker_gwbridge     bridge              local
a7449465c379        host                host                local
8hq1n8nak54x        ingress             overlay             swarm
06c349b9cc77        none                null                local
wlqnvajmmzsk        overnet             overlay             swarm

We can also run docker network inspect overnet on the second terminal to get more detailed information about the “overnet” network and obtain the IP address of the task running on the second terminal.

docker network inspect overnet
[
    {
        "Name": "overnet",
        "Id": "wlqnvajmmzskn84bqbdi1ytuy",
        "Created": "2017-04-04T09:35:47.526642642Z",
        "Scope": "swarm",
        "Driver": "overlay",
        "EnableIPv6": false,
        "IPAM": {
            "Driver": "default",
            "Options": null,
            "Config": [
                {
                    "Subnet": "10.0.0.0/24",
                    "Gateway": "10.0.0.1"
                }
            ]
        },
        "Internal": false,
        "Attachable": false,
        "Containers": {
            "fbc8bb0834429a68b2ccef25d3c90135dbda41e08b300f07845cb7f082bcdf01": {
                "Name": "myservice.1.riicggj5tutar7h7sgsvqg72r",
                "EndpointID": "8edf83ebce77aed6d0193295c80c6aa7a5b76a08880a166002ecda3a2099bb6c",
                "MacAddress": "02:42:0a:00:00:03",
                "IPv4Address": "10.0.0.3/24",
                "IPv6Address": ""
            }
        },
        "Options": {
            "com.docker.network.driver.overlay.vxlanid_list": "4097"
        },
        "Labels": {},
        "Peers": [
            {
                "Name": "node1-f6a6f8e18a9d",
                "IP": "10.0.0.5"
            },
            {
                "Name": "node2-507a763bed93",
                "IP": "10.0.0.6"
            }
        ]
    }
]

You should note that as of Docker 1.12, docker network inspect only shows containers/tasks running on the local node. This means that 10.0.0.3 is the IPv4 address of the container running on the second node. Make a note of this IP address for the next step (the IP address in your lab might be different than the one shown here in the lab guide).

Step 4: Test the network

To complete this step you will need the IP address of the service task running on node2 that you saw in the previous step (10.0.0.3).

Execute the following commands from the first terminal.

docker network inspect overnet
[
    {
        "Name": "overnet",
        "Id": "wlqnvajmmzskn84bqbdi1ytuy",
        "Created": "2017-04-04T09:35:47.362263887Z",
        "Scope": "swarm",
        "Driver": "overlay",
        "EnableIPv6": false,
        "IPAM": {
            "Driver": "default",
            "Options": null,
            "Config": [
                {
                    "Subnet": "10.0.0.0/24",
                    "Gateway": "10.0.0.1"
                }
            ]
        },
        "Internal": false,
        "Attachable": false,
        "Containers": {
            "d676496d18f76c34d3b79fbf6573a5672a81d725d7c8704b49b4f797f6426454": {
                "Name": "myservice.2.nlozn82wsttv75cs9vs3ju7vs",
                "EndpointID": "36638a55fcf4ada2989650d0dde193bc2f81e0e9e3c153d3e9d1d85e89a642e6",
                "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": "node1-f6a6f8e18a9d",
                "IP": "10.0.0.5"
            },
            {
                "Name": "node2-507a763bed93",
                "IP": "10.0.0.6"
            }
        ]
    }
]

Notice that the IP address listed for the service task (container) running is different to the IP address for the service task running on the second node. Note also that they are one the sane “overnet” network.

Run a docker ps command to get the ID of the service task so that you can log in to it in the next step.

docker ps
CONTAINER ID        IMAGE                                                                            COMMAND                  CREATED             STATUS              PORTS                           NAMES
d676496d18f7        ubuntu@sha256:dd7808d8792c9841d0b460122f1acf0a2dd1f56404f8d1e56298048885e45535   "sleep infinity"         10 minutes ago      Up 10 minutes                                       myservice.2.nlozn82wsttv75cs9vs3ju7vs
<Snip>

Log on to the service task. Be sure to use the container ID from your environment as it will be different from the example shown below. We can do this by running docker exec -it <CONTAINER ID> /bin/bash.

docker exec -it yourcontainerid /bin/bash
root@d676496d18f7:/#

Install the ping command and ping the service task running on the second node where it had a IP address of 10.0.0.3 from the docker network inspect overnet command.

apt-get update && apt-get install -y iputils-ping

Now, lets ping 10.0.0.3.

root@d676496d18f7:/# ping -c5 10.0.0.3
PING 10.0.0.3 (10.0.0.3) 56(84) bytes of data.
^C
--- 10.0.0.3 ping statistics ---
4 packets transmitted, 0 received, 100% packet loss, time 2998ms

The output above shows that both tasks from the myservice service are on the same overlay network spanning both nodes and that they can use this network to communicate.

Step 5: Test service discovery

Now that you have a working service using an overlay network, let’s test service discovery.

If you are not still inside of the container, log back into it with the docker exec -it <CONTAINER ID> /bin/bash command.

Run cat /etc/resolv.conf form inside of the container.

docker exec -it yourcontainerid /bin/bash
cat /etc/resolv.conf
search ivaf2i2atqouppoxund0tvddsa.jx.internal.cloudapp.net
nameserver 127.0.0.11
options ndots:0

The value that we are interested in is the nameserver 127.0.0.11. This value sends all DNS queries from the container to an embedded DNS resolver running inside the container listening on 127.0.0.11:53. All Docker container run an embedded DNS server at this address.

NOTE: Some of the other values in your file may be different to those shown in this guide.

Try and ping the “myservice” name from within the container by running ping -c5 myservice.

root@d676496d18f7:/# ping -c5 myservice
PING myservice (10.0.0.2) 56(84) bytes of data.
64 bytes from 10.0.0.2: icmp_seq=1 ttl=64 time=0.020 ms
64 bytes from 10.0.0.2: icmp_seq=2 ttl=64 time=0.052 ms
64 bytes from 10.0.0.2: icmp_seq=3 ttl=64 time=0.044 ms
64 bytes from 10.0.0.2: icmp_seq=4 ttl=64 time=0.042 ms
64 bytes from 10.0.0.2: icmp_seq=5 ttl=64 time=0.056 ms

--- myservice ping statistics ---
5 packets transmitted, 5 received, 0% packet loss, time 4001ms
rtt min/avg/max/mdev = 0.020/0.042/0.056/0.015 ms

The output clearly shows that the container can ping the myservice service by name. Notice that the IP address returned is 10.0.0.2. In the next few steps we’ll verify that this address is the virtual IP (VIP) assigned to the myservice service.

Type the exit command to leave the exec container session and return to the shell prompt of your Docker host.

root@d676496d18f7:/# exit

Inspect the configuration of the “myservice” service by running docker service inspect myservice. Lets verify that the VIP value matches the value returned by the previous ping -c5 myservice command.

docker service inspect myservice
[
    {
        "ID": "ov30itv6t2n7axy2goqbfqt5e",
        "Version": {
            "Index": 19
        },
        "CreatedAt": "2017-04-04T09:35:47.009730798Z",
        "UpdatedAt": "2017-04-04T09:35:47.05475096Z",
        "Spec": {
            "Name": "myservice",
            "TaskTemplate": {
                "ContainerSpec": {
                    "Image": "ubuntu:latest@sha256:dd7808d8792c9841d0b460122f1acf0a2dd1f56404f8d1e56298048885e45535",
                    "Args": [
                        "sleep",
                        "infinity"
                    ],
<Snip>
        "Endpoint": {
            "Spec": {
                "Mode": "vip"
            },
            "VirtualIPs": [
                {
                    "NetworkID": "wlqnvajmmzskn84bqbdi1ytuy",
                    "Addr": "10.0.0.2/24"
                }
            ]
        },
<Snip>

Towards the bottom of the output you will see the VIP of the service listed. The VIP in the output above is 10.0.0.2 but the value may be different in your setup. The important point to note is that the VIP listed here matches the value returned by the ping -c5 myservice command.

Feel free to create a new docker exec session to the service task (container) running on node2 and perform the same ping -c5 service command. You will get a response form the same VIP.

Cleaning Up

Hopefully you were able to learn a little about how Docker Networking works during this lab. Lets clean up the service we created, the containers we started, and finally disable Swarm mode.

Execute the docker service rm myservice command to remove the service called myservice.

docker service rm myservice

Execute the docker ps command to get a list of running containers.

docker ps
CONTAINER ID        IMAGE               COMMAND                  CREATED             STATUS              PORTS                           NAMES
846af8479944        ubuntu              "sleep infinity"         17 minutes ago      Up 17 minutes                                       heuristic_boyd
4e0da45b0f16        nginx               "nginx -g 'daemon ..."   12 minutes ago      Up 12 minutes       443/tcp, 0.0.0.0:8080->80/tcp   web1

You can use the docker kill <CONTAINER ID ...> command to kill the ubunut and nginx containers we started at the beginning.

docker kill yourcontainerid1 yourcontainerid2

Finally, lets remove node1 and node2 from the Swarm. We can use the docker swarm leave --force command to do that.

Lets run docker swarm leave --force.

docker swarm leave --force

Lets also run docker swarm leave --force.

docker swarm leave --force

Congratulations! You’ve completed this lab!