Not possible to ping or reach a container under its local IP

Question

I have setup a simple flask application in a docker container. My docker file is as follows:

FROM python
ADD . /app
WORKDIR /app
RUN pip install -r requirements.txt
CMD ["python", "myFlask.py"]

I start the container using

docker run -d myContainer

I retrieve the internal IP address by

docker exec -ti <containerID> cat /etc/hosts

and it's 172.17.0.2. When I try to ping this address or try to access the REST API using curl I cannot reach it. When I use port forwarding using -p 5000:5000 as part of the run command I can reach the REST API under localhost:5000. I am working under OS X.

Why can't I reach the container under its local IP?

Answer 1

I think I found the answer here: https://docs.docker.com/docker-for-mac/networking/#known-limitations-use-cases-and-workarounds. It's not working under OS X: "Docker Desktop for Mac can’t route traffic to containers."