Configuring IPv6 Networking in Docker and Docker Compose

With the growth of internet-connected devices and the increasing number of connections, IPv6 is becoming more relevant. In this article, I’ll show you how to enable IPv6 support in Docker and Docker Compose to ensure scalability and prepare your infrastructure for future network requirements.

Why Use IPv6?

IPv4 was initially limited to a 32-bit address space, leading to a shortage of available addresses. IPv6 solves this problem by offering a 128-bit address space. Using IPv6 in container infrastructure provides the following benefits:

• Scalability: A vast number of addresses.
• Simplified routing: Improved structure for address aggregation.
• Future compatibility: The internet is gradually shifting to IPv6, and your application should be ready.

Enabling IPv6 Support in Docker

To start, you need to enable IPv6 support in Docker. By default, Docker only supports IPv4, so configuration changes are required.

Step 1: Configure Docker Settings

1. Open or create Docker’s daemon.json configuration file:

sudo nano /etc/docker/daemon.json

2. Add the following lines:

{
  "ipv6": true,
  "fixed-cidr-v6": "2001:db8:abc1::/64"
}

The "ipv6": true parameter enables IPv6 support, and "fixed-cidr-v6" specifies the IPv6 subnet that the Docker network will use.

Step 2: Restart Docker

After making the changes, restart Docker to apply the settings:

sudo systemctl restart docker

Step 3: Verify the Network

Ensure that the IPv6-supported network was created successfully by running:

docker network ls

Then check the network configuration:

docker network inspect bridge

You should see your IPv6 subnet and gateway.

Creating a Container with IPv6 Support

Now that Docker supports IPv6, you can create containers with IPv6 capabilities.

Step 1: Start a Container

Launch a container with IPv6 support:

docker run -di --name alpine6 alpine

Step 2: Check Addresses

Verify that the container has both IPv4 and IPv6 addresses:

docker exec alpine6 ip a

Step 3: Ping the Gateway

Ensure that the container can interact with the network via IPv6:

docker exec alpine6 ping6 2001:db8:abc1::1

Creating a Custom Network with IPv6

Step 1: Create the Network

For production environments, it’s better to create your own network:

docker network create --ipv6 --subnet="2001:db8:1::/64" --gateway="2001:db8:1::1" my-net

Step 2: Connect a Container

Attach the container to the custom network:

docker run -di --name alpine_custom --network my-net alpine

Setting Up IPv6 Networking with Docker Compose

Docker Compose is a powerful tool for managing multi-container applications. You can also configure IPv6 support through Compose.

Example 1: Using an Existing Network

1. First, create the network via the command line:

docker network create --ipv6 --subnet="2001:db8:1::/64" --gateway="2001:db8:1::1" mynetv6

2. Now create a docker-compose.yml file that will use this network:

services:
  app:
    image: alpine:latest
    command: ping6 -c 4 2001:db8:1::1
    networks:
      - mynetv6
networks:
  mynetv6:
    external: true

3. Run Compose:

docker compose up

Example 2: Creating the Network and Container via Docker Compose

Another approach is to manage the network entirely through Compose:

services:
  app:
    image: alpine:latest
    command: ping6 -c 4 2001:db8:a::1
    networks:
      - custom_net
networks:
  custom_net:
    enable_ipv6: true
    ipam:
      config:
        - subnet: 2001:db8:a::/64
          gateway: 2001:db8:a::1

Run:

docker compose up

This file will create a new IPv6-enabled network and launch the container.

Conclusion

IPv6 is becoming an increasingly important component of modern network infrastructure. Now you know how to enable IPv6 support in Docker and Docker Compose, allowing you to create scalable and modern infrastructure for your applications. Regularly test your network settings to ensure that your containers are functioning correctly with IPv6.