Host mode - Amazon Elastic Container Service

Host mode

The host network mode is the most basic network mode that's supported in Amazon ECS. Using host mode, the networking of the container is tied directly to the underlying host that's running the container.

                    Diagram showing architecture of a network with containers using the host
                        network mode.

Assume that you're running a Node.js container with an Express application that listens on port 3000 similar to the one illustrated in the preceding diagram. When the host network mode is used, the container receives traffic on port 3000 using the IP address of the underlying host Amazon EC2 instance. We do not recommend using this mode.

There are significant drawbacks to using this network mode. You can’t run more than a single instantiation of a task on each host. This is because only the first task can bind to its required port on the Amazon EC2 instance. There's also no way to remap a container port when it's using host network mode. For example, if an application needs to listen on a particular port number, you can't remap the port number directly. Instead, you must manage any port conflicts through changing the application configuration.

There are also security implications when using the host network mode. This mode allows containers to impersonate the host, and it allows containers to connect to private loopback network services on the host.

The host network mode is only supported for Amazon ECS tasks hosted on Amazon EC2 instances. It's not supported when using Amazon ECS on Fargate.