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Why is it possible to connect to the redis docker container without port forwarding?

When I run: docker run --rm -it redis, The container receives ip: 172.18.0.2. Then from the host I connect to the container with the following command: redis-cli -h 172.18.0.2, and it connects normally, everything works, the keys are added. Why does this happen without port forwarding? Default docker network – bridge

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3

Answers


  1. 0

    It’s because the redis docker file exposes the right port for the api which is 6379.

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  2. 0

    docker run --rm -it redis will not expose the port. Try stop the redis container. Then run redis-cli -h 172.18.0.2 to check if another redis exists.

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  3. 0

    It is only possible because you’re on native Linux, and the way Docker networking is implemented, it happens to be possible to directly connect to the container-private IP addresses from outside Docker.

    This doesn’t work in a wide variety of common situations (on MacOS or Windows hosts; if Docker is actually running in a VM; if you’re making the call from a different host) and the IP address you get can change if the container is recreated. As such it’s not usually a best practice to look up the container-private IP address. Use docker run -p to publish a port, and connect to that published port and the host’s IP address.

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