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By default, a single network is created by Docker Compose in our application and each container is added there as a service. Every container on the network can be accessed and found by containers on the single network.

We can configure our network by defining network modes in Docker Compose. This article will discuss how to define and set up a network using network modes in Docker Compose.

Collecting network information in Docker

If we want to configure a network mode for a specific container or service, we need to gather additional information first. Running the command docker network lswill allow us to list the current Docker networks.

It should look similar to the output below.

NETWORK ID          NAME                         DRIVER
17cc61428fef        bridge                       bridge
098522f7fce0        sample_default               bridge
1ce3c472afc6        test_default                 bridge
8fd07e456e6c        host                         host
3b5787919641        none                         null

This command will come handy if we have to know the name or ID of our container, service or network through the previous command provided above.

Configuring network mode in Docker Compose

In Docker Compose version 3, we can use network mode in our YAML file by providing network_mode: parameter and its value. So, make sure you specify the Docker compose version we are using using version: parameter and value 3 or 3.0.

example:

version: "3"
services:
  app:
    network_mode: "host"

In the example above, we used the example host as our network mode, but we can specify containers or services instead. From the Docker official documentation, we can use the following multiple values ​​when defining the network mode of a service:

example:

network_mode: "bridge"
network_mode: "host"
network_mode: "none"
network_mode: "service:[service name]"
network_mode: "container:[container name/id]"

Since we gathered the information earlier, we can use the network name or ID when defining the network mode.

example:

network_mode: "container:sample_default"
network_mode: "container:1ce3c472afc6"

Configuring network mode in Docker Swarm

A collection of physical or virtual machines running Docker applications is called a Docker Swarm. The container orchestration solution called Docker Swarm allows users to control many containers distributed across different hosts.

Once a group of machines are clustered together, we can still run the Docker commands we are used to, but the machines in our cluster will now execute them.

Unfortunately, Docker Compose and Swarm do not play well together. Therefore, we need to define the network manually using the networks parameter instead of the network_mode parameter, and it should look like this.

example:

version: "3.0"
services:
    app:
        networks:
            - host

networks:
    host:
        name: [Your Network Mode Value]
        external: true