Learn container networking vocabulary: bridge network, host networking, ClusterIP, DNS between containers, port mapping, network namespaces — the language of professional container networking discussions.
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The engineer says: 'The container is on the bridge network.' What is Docker's bridge network?
The bridge network is Docker's default network driver. When containers are started without specifying a network, they are attached to the default bridge network (docker0). Containers on the same bridge network can communicate with each other using their IP addresses. The bridge is isolated from the host network; outbound traffic goes through NAT. Custom bridge networks also support DNS-based container discovery by container name.
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The developer says: 'We use host networking for this container because it needs direct access to the host's network interfaces.' What is host networking?
In host networking mode (--network=host in Docker), the container shares the host machine's network namespace. The container uses the host's IP address and can bind to host ports directly, with no NAT. This maximises network performance and allows access to host network interfaces, but it eliminates network isolation between the container and the host. It is used for performance-sensitive applications or those requiring raw socket access.
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The Kubernetes engineer explains: 'The service is accessed via the ClusterIP.' What is a ClusterIP?
ClusterIP is the default Kubernetes Service type. It assigns a virtual IP address that is only reachable from within the cluster. Other pods access the service using this stable virtual IP (or the DNS name) rather than connecting directly to pod IPs (which change as pods are rescheduled). ClusterIP is used for internal service-to-service communication where no external access is needed.
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The developer asks: 'How does DNS resolution between containers work in Docker Compose?' What is the answer?
In Docker Compose, when services are on the same user-defined network (which Compose creates by default), Docker's embedded DNS server resolves container names. Each service can reach another by its service name as a hostname (e.g., a web service can connect to 'db:5432'). This name-based resolution is more reliable than IP addresses, which can change between container restarts.
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The container configuration shows: 'ports: - 8080:80'. What does this port mapping mean?
Port mapping (or port publishing) connects a port on the host machine to a port inside the container. The format is HOST_PORT:CONTAINER_PORT. '8080:80' means traffic arriving at port 8080 on the host is forwarded to port 80 inside the container. The container's application listens on port 80; external clients connect to port 8080 on the host. Without port mapping, the container's ports are only accessible from within Docker networks.