I am using docker container for my asp.net core web api application and container is up and running.
Now I am getting docker internal IP address using below command,
docker inspect -f "{{range .NetworkSettings.Networks}}{{.IPAddress}}{{end}}" d986472784cb and getting the IP address as 172.20.0.2.
Now I am not getting any result when hitting below url in browser
http://172.20.0.2/WeatherForecast, seeing ERR_CONNECTION_TIMED_OUT error.
local address https://localhost:32772/weatherforecast is just working fine.
What could be the issue?
The container-private IP simply doesn't work in a variety of common circumstances:
If you're not calling from the same host, the container-private IP won't be reachable at all
If there is a VM involved at all (Docker Toolbox on Windows, Docker Desktop on Windows or Mac), the container-private IP won't be reachable at all
If you're not on the same Docker-internal network, you might not be able to reach the container-private IP
Since it doesn't work in so many environments, I wouldn't recommend looking up this IP address at all: forget that particular docker inspect command exists. From the browser, use your host's IP address or DNS name (or localhost if the containers and browser are on the same system, but not if Docker Toolbox is involved) and the published port number (docker run -p option, Docker Compose ports: option, the first port number from that pair).
You need the port number in the ip address url. http://172.20.0.2:32772/WeatherForecast
Related
I'm trying to better understand docker networking, but I'm confused by the following:
I spin up 2 contains via docker-compose (client, api). When I do this, a new network is created, myapp_default, and each container joins this network. The network is a bridge network, and it's at 172.18.0.1. The client is at 172.18.0.2 and the api is at 172.18.0.3.
I can now access the client at 172.18.0.2:8080 and the api at 172.18.0.3:3000 -- this makes total sense. I'm confused when I publish ports in docker-compose: 8080:8080 on the client, and 3000:3000 on the api.
Now I can access the containers from:
Client at 172.18.0.1:8080, 172.18.0.2:8080, and on the docker0 network at 172.17.0.1:8080
API at 172.18.0.1:3000, 172.18.0.3:8080, and on the docker0 network at 172.17.0.1:3000
1) Why can I access the client and api via the docker0 network when I publish ports?
2) Why can I connect to containers via 172.17.0.1 and 172.18.0.1 at all?
You can only access the container-private IP addresses because you're on the same native-Linux host as the Docker daemon. This doesn't work in any other environment (different hosts, MacOS or Windows hosts, environments like Docker Toolbox where Docker is in a VM) and even using docker inspect to find these IP addresses usually isn't a best practice.
When you publish ports they are accessible on the host at those ports. This does work in every environment (in Docker Toolbox "the host" is the VM) and is the recommended way to access your containers from outside Docker space. Unless you bind to a specific address, the containers are accessible on every host interface and every host IP address; that includes the artificial 172.17.0.1 etc. that get created with Docker bridge networks.
Publishing ports is in addition to the other networking-related setup Docker does; it doesn't prevent you from reaching the containers by other paths.
If you haven't yet, you should also read Networking in Compose in the Docker documentation. Whether you publish ports or not, you can use the names in the docker-compose.yml file like client and api as host names, connecting the the (unmapped) port the actual server processes are listening on. Between this functionality and what you get from publishing ports you don't ever actually need to directly know the container-private IP addresses.
For regular docker containers (say the hello world example), after you run it, it is accessible thought localhost, where you can make a request it through your browser.
But sometimes it seems to access a container you need a special IP address. I'm wondering what's this behavior of docker container networking called and where is it defined/documented.
Let's say my local ip address is 10.0.75.1 (got from Network properties in Windows settings named, vEthernet (DockerNAT)). But in order to connect to a container running I had to use ip address 10.0.75.2. Why is this?
If try to inspect existing docker networks using docker network [cmd], the containers seem to be on different subnets, for example '172.17.0.0/16'
I am using Docker desktop, I have a couple of docker containers running using docker-compose and port forwarding. I can access the containers from my mac using localhost. On the second container, I am exposing on different ports. I can see ip addresses are associated to both containers by using docker inspect, but I cannot access using the ip address.
I would like access the container from my local mac by
dns domain
ip address
Any help appreciated.
Thanks
You cannot directly connect to the container-private IP addresses on MacOS. You also can't connect to them using a VM-based Docker implementation like Docker Toolbox or Kubernetes' minikube, or from a different host. Looking up and using these IP addresses, or trying to manually set them, usually isn't a best practice.
Instead you can use the docker run -p option to publish a port from your container to the host. Programs running directly on the host can access the container using localhost as a host name and the published port number. This works on all platforms; on VM-based solutions use the VM's IP address instead of localhost; from a different host, use the Docker host's DNS name or IP address.
i want to expose the container ip to the external network where the host is running so that i can directly ping the docker container ip from an external machine.
If i ping the docker container ip from the external machine where the machine hosting the docker and the machine from which i am pinging are in the same network i need to get the response from these machines
Pinging the container's IP (i.e. the IP it shows when you look at docker inspect [CONTAINER]) from another machine does not work. However, the container is reachable via the public IP of its host.
In addition to Borja's answer, you can expose the ports of Docker containers by adding -p [HOST_PORT]:[CONTAINER_PORT] to your docker run command.
E.g. if you want to reach a web server in a Docker container from another machine, you can start it with docker run -d -p 80:80 httpd:alpine. The container's port 80 is then reachable via the host's port 80. Other machines on the same network will then also be able to reach the webserver in this container (depending on Firewall settings etc. of course...)
Since you tagged this as kubernetes:
You cannot directly send packets to individual Docker containers. You need to send them to somewhere else that’s able to route them. In the case of plain Docker, you need to use the docker run -p option to publish a port to the host, and then containers will be reachable via the published port via the host’s IP address or DNS name. In a Kubernetes context, you need to set up a Service that’s able to route traffic to the Pod (or Pods) that are running your container, and you ultimately reach containers via that Service.
The container-internal IP addresses are essentially useless in many contexts. (They cannot be reached from off-host at all; in some environments you can’t even reach them from outside of Docker on the same host.) There are other mechanisms you can use to reach containers (docker run -p from outside Docker, inter-container DNS from within Docker) and you never need to look up these IP addresses at all.
Your question places a heavy emphasis on ping(1). This is a very-low-level debugging tool that uses a network protocol called ICMP. If sending packets using ICMP is actually core to your workflow, you will have difficulty running it in Docker or Kubernetes. I suspect you aren’t actually. Don’t worry so much about being able to directly ping containers; use higher-level tools like curl(1) if you need to verify that a request is reaching its container.
It's pretty easy actually, assuming you have control over the routing tables of your external devices (either directly, or via your LAN's gateway/router). Assuming your containers are using a bridge network of 172.17.0.0/16, you add a static entry for the 172.17.0.0/16 network, with your Docker physical LAN IP as the gateway. You might need to also allow this forwarding in your Docker OS firewall configuration.
After that, you should be able to connect to your docker container using its bridge address (172.17.0.2 for example). Note however that it will likely not respond to pings, due to the container's firewall.
If you're content to access your container using only the bridge IP (and never again use your Docker host IP with the mapped-port), you can remove port mapping from the container entirely.
You need to create a new bridge docker network and attach the container to this network. You should be able to connect by this way.
docker network create -d bridge my-new-bridge-network
or
docker network create --driver=bridge --subnet=192.168.0.0/16 my-new-bridge-network
connect:
docker network connect my-new-bridge-network container1
or
docker network connect --ip 192.168.0.10/16 my-new-bridge-network container-name
If the problem persist, just reload docker daemon, restart the service. Is a known issue.
I am having difficulty connecting from the host to an ASP.Net website running in a Windows container on Docker. I can connect to a website running in a Linux container without any problem.
I have tried connecting to both localhost and to the IP port assigned to the container but in both cases I just get a timeout error.
I have tried several ASP.Net examples which are already pre-built along with trying to build my own custom image. In every case I get the same timeout error. I have also tried uninstalling and re-installing docker but that didn't change anything.
I am running Windows 10 Pro and Docker Community Edition Version 17.03.1-ce-win12 (12058)
Ultimately I was able to completely reset my container network using a customized older version of the Microsoft Vitualization cleanup scripts. https://github.com/Microsoft/Virtualization-Documentation/tree/live/windows-server-container-tools/CleanupContainerHostNetworking This reset my container network and everything is now working as expected.
SUMMARY:
When the published port/s for a container are defined using the EXPOSE directive in the container's Dockerfile, the -P argument must be used with the docker run command in order to "activate" those exposed port/s.
It is not possible for a Windows container host to access containers that it is running using localhost, 127.0.0.1 or its external host IP address. Access containers running on a given host, A, by using the IP address of A from a second host, B. Alternatively, you can use the IP address of a container directly.
FULL EXPLANATION:
So there are a few nuances with ensuring that the proper firewall rules are created, and your containers are actually accessible on their published port/s.
For instance, I'll assume that your ASP.Net containerized application is defined by a container image, which was defined by a Dockerfile. If so, you probably defined the published port for the image/app using the Dockerfile EXPOSE directive. In this case, when you actually run the container you need to "activate" that published port using the "-P" argument to the docker run command.
For example, if your container image is web_app, and the Dockerfile for that image included the line, EXPOSE 80, then when you go ahead and run that image you need to do something like:
C:\> docker run -P web_app
Once the container is running, it should be available on container port 80. You can then go ahead and view the app via browser. To do that you have two options:
You can access the app from your container host, using the container IP and port
Find the container IP using docker network inspect nat, then looking for the endpoint/IP address that corresponds with your container.
You can also fund the container IP by running docker exec <CONTAINER ID> ipconfig, where <CONTAINER ID> is the ID of your container.
You can get the ID of your container and the exposed port for your container by running docker ps on the container host.
You can access the app from another host machine, using the container host IP and host port
You can find the IP address of your host using ipconfig.
You can identify the host port upon which your app is exposed, by running docker ps from the host. Then, under PORTS you'll see a mapping of the form 0.0.0.0:<HOST PORT>-><CONTAINER PORT>/TCP. In this mapping <HOST PORT>, is the port upon which your app is available on the host.
Once you have the IP address of your container host, and the port upon which your app is available on the host, you can use that information to access your app from a browser on a separate host.
NOTE: Today you cannot access a container in this way from its own host--currently a Windows container host cannot access the containers it is running, despite whether localhost, 127.0.0.1 or the host IP address is used.