Docker-toolbox cannot access VM by IP

Question

I run: docker run -p "9999:80" nginx and attempt to access the web server using the following address: 172.17.0.2:9999. I got this IP from docker inspect [container_id]:

 "NetworkSettings": {
    "Bridge": "",
    "SandboxID": "877eb750a0f35037f0b9dff2b6bd95f7dd4aaf80ae0ed8cf65e20ad8aeb85132",
    "HairpinMode": false,
    "LinkLocalIPv6Address": "",
    "LinkLocalIPv6PrefixLen": 0,
    "Ports": {
        "80/tcp": [
            {
                "HostIp": "0.0.0.0",
                "HostPort": "9999"
            }
        ]
            },
            "SandboxKey": "/var/run/docker/netns/877eb750a0f3",
            "SecondaryIPAddresses": null,
            "SecondaryIPv6Addresses": null,
            "EndpointID": "2599dc8c2311725e9816fc30e60a86550cb42887871a921365e3df866427464e",
            "Gateway": "172.17.0.1",
            "GlobalIPv6Address": "",
            "GlobalIPv6PrefixLen": 0,
            "IPAddress": "172.17.0.2",
            "IPPrefixLen": 16,
            "IPv6Gateway": "",
            "MacAddress": "02:42:ac:11:00:02",
            "Networks": {
                "bridge": {
                    "IPAMConfig": null,
                    "Links": null,
                    "Aliases": null,
                    "NetworkID": "ffc037f862047b118824b8d322aab771ba75a009881959461be577ffebb42a80",
                    "EndpointID": "2599dc8c2311725e9816fc30e60a86550cb42887871a921365e3df866427464e",
                    "Gateway": "172.17.0.1",
                    "IPAddress": "172.17.0.2",
                    "IPPrefixLen": 16,
                    "IPv6Gateway": "",
                    "GlobalIPv6Address": "",
                    "GlobalIPv6PrefixLen": 0,
                    "MacAddress": "02:42:ac:11:00:02",
                    "DriverOpts": null
                }
            }
        }

But this doesn't work as expected. If I ping 172.17.0.2 from the host I get no response.

Any ideas what's going wrong? It's so much hassle with docker-toolbox because my version of Windows 10 isn't supported by docker.

Answer 1

Since you launched the container with docker run -p 9999:80, you can reach it on the VM's IP address on the public port 9999. docker-machine ip will tell you that IP address (but it is usually 192.168.99.100). So try http://192.168.99.100:9999/ as a URL to reach the container.

The container-internal IP addresses aren't especially useful. One significant problem with them is that they can't be reached from other hosts. In the case of a Docker Toolbox environment, everything Docker-related actually runs inside a virtual machine, and your host system counts as "other hosts" for this. Also note that if you do have occasion to use it (or more often use inter-container DNS for one container to reach another by its docker run --name) you need the port the server is listening on inside the container, not the published port: from another container you might use http://nginx_container_name:80/.