How to get all ip addresses on a docker network? - docker

Question

I have containers running in a swarm stack of services (on different docker-machines each) connected together on an overlay docker network.
How would it be possible to get all used ip adresses on the network associated with their services or container name from inside a container on this network?
Thank you

Answer 1

If you want to execute this command from inside containers, first you have to mount docker.sock for each service (assuming that docker is installed in the container)
volumes:
- /var/run/docker.sock:/var/run/docker.sock
then in each container you have to install jq and after that you can simply run docker network inspect <network_name_here> | jq -r 'map(.Containers[].IPv4Address) []' expected output something like:
172.21.0.2/16
172.21.0.5/16
172.21.0.4/16
172.21.0.3/16

Answer 2

Find the name OR ID of overlay network -
$ docker network ls | grep overlay
Do a inspect -
docker inspect $NETWORK_NAME
You will be able to find the container names & IPs allocated to them. You can do a fetch/grep the required values from the inspect output. You will find the output something as below -
"IPAM": {
"Driver": "default",
"Options": null,
"Config": [
{
"Subnet": "172.23.0.0/16",
"Gateway": "172.23.0.1"
}
]
},
"Internal": false,
"Attachable": true,
"Ingress": false,
"ConfigFrom": {
"Network": ""
},
"ConfigOnly": false,
"Containers": {
"183584efd63af145490a9afb61eac5db994391ae94467b32086f1ece84ec0114": {
"Name": "emailparser_lr_1",
"EndpointID": "0a9d0958caf0fa454eb7dbe1568105bfaf1813471d466e10030db3f025121dd7",
"MacAddress": "02:42:ac:17:00:04",
"IPv4Address": "172.23.0.4/16",
"IPv6Address": ""
},
"576cb03e753a987eb3f51a36d4113ffb60432937a2313873b8608c51006ae832": {
"Name": "emailparser",
"EndpointID": "833b5c940d547437c4c3e81493b8742b76a3b8644be86af92e5cdf90a7bb23bd",
"MacAddress": "02:42:ac:17:00:02",
"IPv4Address": "172.23.0.2/16",
"IPv6Address": ""
},

Answer 3

Assuming you're using the default VIP endpoint, you can use DNS to resolve the IP's of a service. Here's an example of using dig to get VIP IP using and then get the individual container IP's behind that VIP using tasks.
docker network create --driver overlay --attachable sweet
docker service create --name nginx --replicas=5 --network sweet nginx
docker container run --network sweet -it bretfisher/netshoot dig nginx
~~~
;; ANSWER SECTION:
nginx. 600 IN A 10.0.0.3
~~~
docker container run --network sweet -it bretfisher/netshoot dig tasks.nginx
~~~
;; ANSWER SECTION:
tasks.nginx. 600 IN A 10.0.0.5
tasks.nginx. 600 IN A 10.0.0.8
tasks.nginx. 600 IN A 10.0.0.7
tasks.nginx. 600 IN A 10.0.0.6
tasks.nginx. 600 IN A 10.0.0.4
~~~

Answer 4

for n in `docker network ls | awk '!/NETWORK/ {print $1}'`; do docker network inspect $n; done

Answer 5

First, find the name of the network which your swarm is using.
Then run docker network inspect <NETWORK-NAME>. This will give you a JSON output, in which you'll find an object with key "Containers". This object reveals all the containers in the network and their IP addresses respectively.