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A Comprehensive Guide To Docker Networking

27th Sep, 2023
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    A Comprehensive Guide To Docker Networking

    With its powerful networking infrastructure encapsulation, Docker brings application mobility, reduces dependence on host network settings, and facilitates effortless container transport across computers. Additionally, Docker Networking plays a vital role in enabling seamless communication and secure interaction between containers and the outside world. In this guide, we delve into the intricacies of Docker networking, uncovering its benefits, best practices, and techniques to empower you with the knowledge for reliable and scalable software development.

    Understanding Docker networking is fundamental in modern software development and DevOps practices. If you're interested in diving deeper into Docker and related technologies, consider enrolling in a Docker and Kubernetes certification course offered by KnowledgeHut.

    What is Docker Networking?

    Docker Networking is a functionality inherent to Docker that enables the creation of bespoke network segments, thereby facilitating inter-container communication and communication with external systems. The feature above offers users high adaptability in creating and implementing their software programmes. It is also used enormously in DevOps. We can also say that Docker is the first part in learning DevOps, checkout our comprehensive DevOps course, to learn about DevOps and other technology that uses docker.

    Docker instantiates a distinct and self-contained network on the underlying host system and designates a series of IP addresses to it. IP addresses are assigned to containers created within this network, enabling them to communicate with each other and external entities. In this article you will find the key concepts to all the way to examples. So, welcome to the docker networking explained.

    Key concepts in Docker Networking:

    Before knowing how to create a docker network, it is important to know the key concepts of it. When we understand the basics and important topics like what is docker network, how to create one and how secure it, one can go and create network with its amazing capability.

    Network Drivers: Docker networking utilises multiple network drivers to cater to diverse requirements. Docker offers a set of primary network drivers, drivers in docker network list are:

    • Bridge: The Bridge network driver is the preconfigured and standard option. In the absence of a specified driver, Docker will automatically assign one. This software solution is well-suited for use as a standalone application.
    • Host: The driver facilitates the elimination of network isolation between the Docker host and Docker containers. In certain scenarios, it may prove advantageous to avoid port mapping execution.
    • Overlay: The purpose of this driver is to establish a distributed network among numerous Docker daemon hosts. This feature proves to be advantageous when establishing a swarm or constructing a network that involves multiple hosts.
    • Macvlan: The utilisation of Macvlan networks enables the allocation of a unique MAC address to a container, thereby presenting it as a tangible device on the network.
    • None: This driver is designed for network usage without any network isolation.

    Docker Networking Types: Docker offers four distinct network types, namely Bridge networks, Host networks, Overlay networks, and None networks. Each option serves a specific purpose and can be utilised in various situations based on the application’s requirements.

    The Container Network Model (CNM) is the networking architecture native to Docker. The CNM has been engineered to function seamlessly across single-host and multi-host networking environments. The system comprises three primary elements: the Sandbox, the Endpoint, and the Network.

    Network Plugins: Docker can accommodate third-party network plugins, which enables users to utilise their preferred networking solutions. The enhanced Docker Networking functionality offers increased flexibility and adaptability.

    Goals of Docker Networking 

    Here we will discuss the objectives of Docker Networking:

    • Simplicity: Docker networking is simple. Connects containers—shocking! Allowing children to communicate—what a joyful discovery! For apps with several containers, each has a job and must function together. Microservices are stars in their containers. To create a seamless app, they must communicate!
    • Isolation: It isolates networks. Docker networking isolates networks from interference and conflict. Nets cover each box. Disliked host. Each container's stack is free—no sharing! Container security requires network isolation. Containers using the same ports can't conflict.
    • Interoperability helps containers grow. External networks and services make communication easy—no need to walk! Integrating matters. Containers, systems, Internet resources. Ensure they can comply! Container interoperability is amazing! They can be, Public cloud-based app!
    • Portability: Docker's ability to package a programme and its dependencies into a container and start it on any Docker machine is its main benefit. Docker networking handles container networking while shifting hosts. It lets containers maintain their network settings and connections across host systems.
    • Scalability: Docker networking helps applications scale. Docker networking simplifies networking between containers as applications grow. In dynamic environments like microservices architectures or Kubernetes, containers are created and destroyed often.
    • Flexibility: Docker allows bespoke network plugins and multiple networking choices. This lets you define a networking setup for your application.

    Types of Docker Networks 

    Docker has specialized networking drivers. Docker network types:

    • Bridge Network: The container's default. The default bridge network connects new containers without network specifications. Docker creates a host-private bridge network. Once ports are mapped during container formation time, all containers on this network can communicate directly with each other but only with the host machine or outside world.
    • Host Network: Docker hosts the network stack of a container using the host network mode. The container shares the host's network namespace and can directly connect to host-port services. No NAT translations provide the container good network performance, but it loses network isolation.
    • Overlay Network: The overlay network driver creates a distributed network over many Docker daemon servers, making it ideal for swarm services or containers that must communicate across multiple Docker hosts or clusters. Docker Swarm and multi-host systems require this.
    • Macvlan Network: Containers look like MAC-addressed devices in this network. It lets containers look like network devices to the rest of the network, which may help integrate them into existing networks. Containers have host-accessible IP addresses.

    The none network adds a container to a container-specific network stack without configuring it. The container has a network interface (eth0) but no IP address. It helps create a container without network interfaces. A Docker-based application must choose the right network type for each service. Docker supports network plugins, so you can develop or use a network driver to fulfil your networking needs.

    Customise Docker networking via plugins. These plugins integrate Docker networks with various networking systems. Popular Docker network example plugins include:

    • Weave: A virtual network connects Docker containers on separate hosts or clouds. It requires no setup or hardware. Weave networks are partition-tolerant, resilient, and ideal for uncertain environments.
    • Networking and policy provider Calico. Connect containers, virtual machines, and bare-metal servers. It is simple, scalable, and effective for network policy implementation. Calico is ideal for Kubernetes networking since it enforces network policies.
    • Flannel: A Kubernetes container network fabric. It connects containers on different hosts. Each host's containers use Flannel's subnet for IP addresses. Simple Kubernetes networking.
    • Cilium: This Linux container framework plugin adds API-aware network security filtering to Docker and Kubernetes. It simplifies and powerfully enforces network-layer and application-layer security policies based on container/pod identities.
    • Contiv: Flexible networking (native L3 utilising BGP, overlay using vxlan, standard L2, or Cisco-SDN/ACI) provides varied use cases. Cisco built it.

    Use case and needs determine network plugin selection. Consider deployment size, isolation level, networking equipment, and unique network policy requirements.

    Basic Docker Networking Commands

    • List Networks: The docker network ls command will list all the networks that are currently available in your Docker environment.

    docker network ls

    • Inspect a Network: The docker network inspect command allows you to view detailed information about a network.

    docker network inspect [network name or id]

    • Create a Network: The docker network create command allows you to create a new network. You can specify the driver for the web (default is a bridge), the name, and other options.

    docker network create --driver bridge my_custom_network

    • Remove a Network: The docker network rm command allows you to remove a network. Be aware that you cannot remove a network that has active containers connected to it.

    docker network rm [network name or id]

    • Connect a Container to a Network: The docker network connect command allows you to connect an existing container to a network.

    docker network connect [network name or id] [container name or id]

    • Disconnect a Container from a Network: The docker network disconnect command allows you to disconnect a container.

    docker network disconnect [network name or id] [container name or id]

    These commands are fundamental to managing Docker networks. They allow you to view, create, and manage the networks and their connections to your containers. Understanding these commands can be useful when setting up a multi-container Docker environment.

    Docker networking is essential for the communication of containerized applications, but it can also offer difficulties. For instance, a frequent problem is that containers can't talk to one another. If they aren't connected to the same network, this could happen. This problem can be fixed by connecting running containers to a custom network.

    The 'host unreachable' problem may also occur inside a container. The restrictions of the firewall may be to blame. If you suspect the firewall is to blame for the problem, temporarily turning it off is a good place to start troubleshooting.

    By learning the differences between bridge, host, and none networks, connectivity problems can be avoided. For instance, a container can use the 'host' network mode to communicate with the host computer.

    The 'docker network inspect' tool is useful for debugging issues because it reveals information about the network.

    Finally, if you are having problems with your network's performance, you may want to switch to network plugins that better fit your needs.

    In most cases, the problem may be solved by learning more about Docker networking fundamentals and taking a methodical approach to verifying network connections.

    Network Drivers 

    Docker network drivers provide the networking capabilities required to support the various communication pathways between containers. Docker includes a number of built-in network drivers, each with unique characteristics that can be selected based on the requirements of your application.

    Here's a quick rundown of the many network drivers available in Docker:

    • Bridge: The Docker container's default network driver. When you start a new Docker container without specifying any network parameters, it connects to a bridge network by default. This driver creates an internal private network for the host, allowing containers to communicate directly with one another and with the host.
    • Host: The host network driver removes network isolation between the Docker host and the Docker containers, allowing the containers to utilise the host’s networking directly. It is a high-performance choice because there is no network between Docker containers and the system.
    • Overlay: The overlay network driver establishes a dispersed network among many Docker daemon hosts. It enables decentralised networks and is especially well-suited for Docker swarm services and multi-host networking.
    • Macvlan: By assigning a MAC address to each container's network interface, Macvlan networks enable containers to appear as physical devices with their own MAC addresses. This allows the container to look like a physical device and function similarly to a physical network interface card.
    • None: This network driver turns off all networking. Typically used in tandem with a custom network driver.

    It's also worth noting that you can install and use third-party network drivers. These network drivers can be used when creating a new docker network create command or launching a new container with the docker run command.

    Container Network Model (CNM) 

    CNM is an abbreviation for Container Network Model. It is a Docker-native method for allowing several containers to communicate across a network. The CNM is an abstract model that specifies a set of rules for managing networking components in order to provide a uniform development experience across platforms and settings.

    The CNM is comprised of three major components:

    • Sandbox: A Sandbox in the CNM separates network settings for a single container or a group of containers. This comprises interface, routing, and DNS configuration management.
    • Endpoint: In the CNM, an endpoint is a network interface in a Sandbox. Each endpoint is connected to the same network and Sandbox.
    • Network: In the CNM, networks are logical entities that group endpoints to provide a layer of isolation. Networks are the components Docker network drivers offer (such as bridge, overlay, and so on).

    The CNM provides a robust and flexible container networking mechanism with this design. It supports many networking solutions, from simple single-host communication to complicated multi-host, multi-network topologies. It also makes pluggable network drivers possible, allowing third-party plugins to increase Docker networking capabilities.

    Docker network security considerations 

    Consider network security when deploying Docker containers:

    Docker isolates networks. This prevents malware from spreading laterally. This isolation is only as good as your network. Check your networks. Otherwise, you risk enabling unwanted traffic. docker network advantages and disadvantages can be decided by how we maintain security in its network. Hence, it is important to look into security of the network before any sensitive production apps that use this technology.

    1. Exposing Ports: Docker containers communicate via network ports. Your programs need open ports, but attackers can use them. Check the open ports and their traffic.

    2. Network Policies: Docker containers communicate using network policies. Limiting your containers' network access to the minimum necessary is crucial.

    3. Encryption: Use Docker's overlay network driver to encrypt sensitive traffic between Docker hosts. This prevents data theft in transit.

    4. Updates and patches: Update Docker and its dependencies to the latest security updates. Docker containers share the host kernel, therefore kernel vulnerabilities can affect all containers on that host.

    5. Third-Party Images: Docker Hub and other public registries may include harmful code. Use Docker's content trust feature to sign and validate images from trusted sources.

    6. Limit privileges: Docker lets you restrict Linux privileges in containers for added security. Block containers from modifying network configuration.

    Security requires constant analyses and updates. Consider adding security tools to monitor your Docker environment for compromise.


    Docker networking is essential for optimal use. Developers and system administrators can design and optimise containerized application communication routes using Docker's networking technology.

    Docker gives you the tools to build the network you need, whether it's isolated with the default bridge driver, direct connections with the host driver, or complicated multi-host networks with the overlay driver. Docker networking plugins enable collaboration with other common networking technologies, resulting in a reliable way to orchestrating and regulating container connections in various contexts.

    To gain practical experience in Docker networking, consider enrolling in the Docker and Kubernetes certification course KnowledgeHut offers. With hands-on training, this course will help you deepen your understanding of Docker networking, among other key DevOps topics.

    Finally, Docker networking is crucial to container management. Inter-container communication makes complex multi-container systems possible. Docker networking lets developers and administrators customise network environments for their applications.

    Software development and IT operations will benefit from Docker networking knowledge as we go towards complex, distributed systems.

    Frequently Asked Questions (FAQs)

    1How can I connect containers running on different Docker hosts?

    Docker's overlay network driver facilitates containers to connect across different Docker hosts. An overlay network is a network that spans multiple Docker hosts and enables their containers to communicate seamlessly. It's widely used in Docker Swarm, a native clustering and scheduling tool for Docker.

    2How can I expose container ports to the host system?

    Docker provides the -p or --publish flag with the docker run command to expose a container's port to the host system. By specifying the host port and the container port in the format -p <host-port>:<container-port>, you can map a port inside the container to a port on the Docker host.

    3How do I link containers for communication in Docker?

    In Docker, containers within the same network can communicate with each other directly using the container name as the hostname. You can use the docker network connect command to connect containers to the same network to enable this communication. Note that Docker's --link option is a legacy feature, and its use is discouraged in favour of user-defined networks.

    4Can I connect Docker containers to external networks?

    Yes, Docker containers can connect to external networks. One way to achieve this is using the Macvlan network driver, which makes containers appear as physical hosts on the web, each with its own MAC and IP address attached to the physical network. Alternatively, you can use the host network driver, which eliminates the network isolation between the Docker host and the containers.


    Vishruth Harithsa


    Vishruth Haritsa is a technologist who wishes to code innovation with quality of passion. He is currently working as a Program Manager at Dynatrace. By hobby, he is a reader of self-improvement books, a Podcaster, a YouTuber and a Teacher who loves to teach the younger generation about technology. His mission statement is to help others get the best out of themselves.

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