Docker Networking
Hi, welcome to the Networking lab for DockerCon 2017!
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:
Document conventions
When you encounter a phrase in between < and > you are meant to substitute in a different value.
For instance if you see ssh <username>@<hostname> you would actually type something like ssh ubuntu@node0-a.ivaf2i2atqouppoxund0tvddsa.jx.internal.cloudapp.net
You will be asked to SSH into various nodes. These nodes are referred to as node0-a, node1-b, node2-c, etc.
Prerequisites
This lab requires two Linux nodes with Docker 17.03 (or higher) installed.
Also, please make sure you can SSH into the Linux nodes. If you haven’t already done so, please SSH in to node0-a and node1-b.
$ ssh ubuntu@<node0-a IP address>
and
$ ssh ubuntu@<node1-b IP address>
Section #1 - Networking Basics
Step 1: The Docker Network Command
If you haven’t already done so, please SSH in to node0-a.
$ ssh ubuntu@<node0-a IP address>
The docker network command is the main command for configuring and managing container networks. Run the docker network command from node0-a.
$ 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 on node0-a 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> on node0-a 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 inspectcommand isdocker 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 on node0-a 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 command on node0-a.
$ 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 on node0-a.
$ sudo apt-get install bridge-utils
Then, list the bridges on your Docker host, by running brctl show on node0-a.
$ 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 on node0-a 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 on node0-a 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 on node0-a.
$ 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 on node0-a.
$ 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 on node0-a, 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> on node0-a. 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.docker.com.
First, we need to get the ID of the container started in the previous step. You can run docker ps on node0-a 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 on node0-a.
$ docker exec -it 846af8479944 /bin/bash
root@846af8479944:/#
Next, we need to install the ping program. So, lets run apt-get update && apt-get install -y iputils-ping.
root@846af8479944:/# apt-get update && apt-get install -y iputils-ping
Lets ping www.docker.com by running ping -c5 www.docker.com
root@846af8479944:/# ping -c5 www.docker.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.
root@846af8479944:/# exit
We should also stop this container so we clean things up from this test, by running docker stop <CONTAINER ID> on node0-a.
$ docker stop 846af8479944
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 on node0-a.
$ 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 on node0-a.
$ 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 on node0-a.
$ 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 on node0-a.
$ docker swarm init
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.
If you haven’t already done so, please SSH in to node1-b.
$ ssh ubuntu@<node0-a IP address>
Copy the entire docker swarm join ... command that is displayed as part of the output from your terminal output on node0-a. Then, paste the copied command into the terminal of node1-b.
$ 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 on node0-a to verify that both nodes are part of the Swarm.
$ docker node ls
ID HOSTNAME STATUS AVAILABILITY MANAGER STATUS
ijjmqthkdya65h9rjzyngdn48 node1-b Ready Active
rzyy572arjko2w0j82zvjkc6u * node0-a 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 on node0-a.
$ 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 node1-b
$ 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 node0-a.
$ 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 node0-a 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 node1-b Running Running about a minute ago
nlozn82wsttv myservice.2 ubuntu:latest node0-a 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 node1-b is running a task on the “overnet” network it will be able to see the “overnet” network. Lets run docker network ls from node1-b 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 node1-b to get more detailed information about the “overnet” network and obtain the IP address of the task running on node1-b.
$ 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": "node0-a-f6a6f8e18a9d",
"IP": "10.0.0.5"
},
{
"Name": "node1-b-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 node1-b. 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 node1-b that you saw in the previous step (10.0.0.3).
Execute the following commands from node0-a.
$ 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": "node0-a-f6a6f8e18a9d",
"IP": "10.0.0.5"
},
{
"Name": "node1-b-507a763bed93",
"IP": "10.0.0.6"
}
]
}
]
Notice that the IP address listed for the service task (container) running on node0-a is different to the IP address for the service task running on node1-b. Note also that they are one the sane “overnet” network.
Run a docker ps command to get the ID of the service task on node0-a 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 d676496d18f7 /bin/bash
root@d676496d18f7:/#
Install the ping command and ping the service task running on node1-b where it had a IP address of 10.0.0.3 from the docker network inspect overnet command.
root@d676496d18f7:/# 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 on node0-a, log back into it with the docker exec -it <CONTAINER ID> /bin/bash command.
Run cat /etc/resolv.conf form inside of the container on node0-a.
$ docker exec -it d676496d18f7 /bin/bash
root@d676496d18f7:/# 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 node0-a 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 node1-b 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 on node0-a to remove the service called myservice.
$ docker service rm myservice
Execute the docker ps command on node0-a 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 on node0-a to kill the ubunut and nginx containers we started at the beginning.
$ docker kill 846af8479944 4e0da45b0f16
Finally, lets remove node0-a and node1-b from the Swarm. We can use the docker swarm leave --force command to do that.
Lets run docker swarm leave --force on node0-a.
$ docker swarm leave --force
Lets also run docker swarm leave --force on node1-b.
$ docker swarm leave --force
Congratulations! You’ve completed this lab!