Nimendra's Notes 🪴

Bridge Interface & Docker Bridge

2 min read

kubernetes kubernetes/networking

Core Idea

A Linux bridge is a virtual switch in the kernel, and Docker builds container networking on top of it: docker0 for the default network and br-* bridges for custom ones.

  • The Linux bridge interface and where its documentation lives.
  • Docker Bridge: the default docker0 bridge.
  • Custom docker network bridges, shown with a named br- example.

Linux Bridge Interface

networking:bridge
08. Docker Networking > Single host Bridge networks

The bridge interface allows system administrators to create multiple layer 2 networks on a single.
In other words, the bridge functions like a network switch between network interfaces on a host, seamlessly connecting them.

Network Namespaces & Veth

Docker Bridge

The two interfaces, docker0 and br-944b28187632, are both virtual bridges used by Docker, but they serve different purposes.

1. docker0 (Default Docker Bridge)

4: docker0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN mode DEFAULT group default
    link/ether 02:42:10:78:2b:c6 brd ff:ff:ff:ff:ff:ff
  • docker0 is the default bridge created by Docker when it is installed.
  • It provides networking for containers using the default bridge network.
  • Containers attached to docker0 can communicate with each other using private IPs in the 172.17.0.0/16 range.
  • NO-CARRIER and state DOWN indicate that no containers are currently running in the default bridge network.

2. br-944b28187632 (Custom Docker Network Bridge)

5: br-944b28187632: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN mode DEFAULT group default
    link/ether 02:42:d7:c7:36:ae brd ff:ff:ff:ff:ff:ff
  • This bridge (br-944b28187632) is a user-defined Docker bridge network.
  • When you create a custom bridge network in Docker (docker network create mynetwork), it generates a new bridge interface with a unique name (like br-944b28187632).
  • Containers connected to this custom network can communicate separately from docker0.
  • NO-CARRIER and state DOWN indicate no containers are currently using this network.

Graph View