diff --git a/docs/reference/glossary.md b/docs/reference/glossary.md index faaa0ea070..f829ad54c0 100644 --- a/docs/reference/glossary.md +++ b/docs/reference/glossary.md @@ -32,6 +32,28 @@ An image that has no parent is a **base image**. [boot2docker](http://boot2docker.io/) is a lightweight Linux distribution made specifically to run Docker containers. The boot2docker management tool for Mac and Windows was deprecated and replaced by [`docker-machine`](#machine) which you can install with the Docker Toolbox. +## bridge + +In terms of generic networking, a bridge is a Link Layer device which forwards +traffic between network segments. A bridge can be a hardware device or a +software device running within a host machine's kernel. + +In terms of Docker, a bridge network uses a software bridge which allows +containers connected to the same bridge network to communicate, while providing +isolation from containers which are not connected to that bridge network. +The Docker bridge driver automatically installs rules in the host machine so +that containers on different bridge networks cannot communicate directly with +each other. + +The default bridge network, which is also named `bridge`, behaves differently +from user-defined bridge networks. Containers connected to the default `bridge` +network can communicate with each other across the bridge by IP address but +cannot resolve each other's container name to an IP address unless they are +explicitly linked using the `--link` flag to `docker run`. + +For more information about Docker networking, see +[Understand container communication](https://docs.docker.com/engine/userguide/networking/default_network/container-communication/). + ## btrfs btrfs (B-tree file system) is a Linux [filesystem](#filesystem) that Docker