br

Start and navigate the current directory tree interactively

$ br

$ br [[-s|--sizes]]

$ br [[-p|--permissions]]

$ br [[-f|--only-folders]]

$ br [[-h|--hidden]]

brctl command [bridge] [interface] [options]

Common commands include:
brctl addbr <bridge>
brctl delbr <bridge>
brctl show
brctl addif <bridge> <interface>
brctl delif <bridge> <interface>
brctl stp <bridge> {on|off}
brctl setageing <bridge> <time>

addbr
    Creates a new Ethernet bridge named <bridge>.

delbr
    Deletes the specified Ethernet bridge named <bridge>.

show
    Lists all existing bridges and their associated interfaces, providing a summary of their configuration.

addif
    Adds the network interface <interface> to the bridge <bridge>. This makes the interface part of the bridged network.

delif
    Removes the network interface <interface> from the bridge <bridge>.

stp {on|off}
    Enables or disables Spanning Tree Protocol (STP) on the bridge <bridge>. STP prevents network loops.

setageing
    Sets the MAC address aging time (in seconds) for the bridge's forwarding database. MAC entries older than this time are removed.

showstp
    Displays detailed Spanning Tree Protocol (STP) information for a specified bridge.

The command br is not a standard Linux command.
This analysis assumes br is a common typo for brctl, the bridge control utility.

brctl is used to set up, maintain, and inspect Ethernet bridges in Linux. An Ethernet bridge acts as a software-defined network switch, allowing multiple network interfaces (physical or virtual) to be combined into a single logical interface. This enables communication between devices connected to different interfaces as if they were on the same physical network segment.

It is commonly employed in virtualization environments (e.g., KVM, LXC) to connect virtual machines or containers to the host network, enabling them to share network access or communicate with each other. It also supports Spanning Tree Protocol (STP) to prevent network loops and various parameters to fine-tune bridge behavior.

The command br itself is not a standard, standalone utility in most mainstream Linux distributions. This analysis covers brctl, which is the likely intended command.

Usage of brctl typically requires root privileges (e.g., using sudo). While still widely used and effective, some newer Linux network configurations, particularly with the iproute2 suite (e.g., using ip link add type bridge), offer alternative and often more integrated ways to manage network bridges.

An Ethernet bridge in Linux is a software implementation of a network switch. It operates at Layer 2 (Data Link Layer) of the OSI model. Its primary function is to forward network traffic between different connected network segments (interfaces) based on MAC addresses, effectively joining them into a single, larger logical network. This is fundamental for scenarios like virtual machine networking, where virtual network interfaces need to connect seamlessly to the host's physical network or to each other.

The brctl utility is part of the bridge-utils package, which has been a staple in Linux networking for many years. It was the primary tool for managing software Ethernet bridges on Linux systems. With the advent of the iproute2 suite, which introduced commands like ip link, modern Linux systems offer alternative and often more unified methods for network configuration. Despite this, brctl remains widely used and is still installed by default on many distributions due to its direct and simple interface for common bridge operations.

ip(8), bridge-utils(8), ifconfig(8), netplan(5)