Скачать или смотреть How to Forward Ports from Host IPs to Specific Container IPs Using Docker Compose

Learn how to effectively forward traffic from specific host IPs to designated container IPs using Docker Compose, and manage port forwarding with iptables.
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Forwarding Ports from Host IPs to Specific Container IPs Using Docker Compose

Docker Compose is a powerful tool for defining and running multi-container Docker applications. However, users often encounter challenges when trying to forward ports from multiple host IPs to specific container IPs. In this guide, we’ll explore how to solve this issue effectively, breaking it down into simple, manageable steps.

Understanding the Problem

When working with containers connected to multiple networks, you may want to direct traffic from different network interfaces of the host to specific IP addresses assigned to the containers. For example:

Assuming you have a container set up with two external IPs (e.g., 1.1.1.1 and 2.2.2.2).

Your host might have two NICs (Network Interface Cards) with IP addresses (3.3.3.3 and 4.4.4.4).

You want to forward HTTP traffic (port 80) from 3.3.3.3 to 1.1.1.1 and from 4.4.4.4 to 2.2.2.2.

The challenge arises because using the ports option in your Docker Compose file does not permit you to specify which container interface the traffic should be forwarded to.

Implementing the Solution

Step 1: Disable Ports Mapping in Docker Compose

Instead of using the ports key within your docker-compose.yaml file, you will need to exclude this option since Docker defaults to forwarding to the first interface. Here’s what your Docker Compose service definition should look like:

[[See Video to Reveal this Text or Code Snippet]]

Step 2: Set Up iptables Rules Manually

Next, you will need to manually add iptables rules to manage the port forwarding. Access your terminal and execute the following commands:

Forward traffic from your host's 3.3.3.3 to the container's 1.1.1.1:

[[See Video to Reveal this Text or Code Snippet]]

Forward traffic from your host's 4.4.4.4 to the container's 2.2.2.2:

[[See Video to Reveal this Text or Code Snippet]]

Step 3: Understanding Container Communication

It’s important to note that communication from your container back to the host is managed by the routing table within the container. Typically, the default route is set to eth0, but this shouldn’t cause any issues due to Docker creating MASQUERADE rules for all container addresses.

This means responses from your container will reach the host without any additional configuration as long as the routes are correctly set.

Conclusion

Forwarding ports from specific host IPs to designated container IPs in Docker Compose can seem daunting at first, but by following these steps, you can manage it effectively. With iptables, you gain control over how traffic is directed, allowing for streamlined communication between your host and containers.

If you have other questions or need further assistance with Docker Compose, feel free to reach out or leave a comment below!