addbr

addbr is a Linux command used to create a new software bridge device. A bridge operates at the data link layer to connect multiple network interfaces as a single broadcast domain, which is useful for virtualization, container networking, and multiport LAN setups. The tool is part of bridging utilities that manage virtual network devices on Linux.

Historically, addbr is provided by the bridge-utils package and is commonly implemented as a wrapper around the brctl addbr command. Modern Linux systems often support the same operation through the iproute2 toolkit, where a bridge can be created with alternatives such as ip link add name BRNAME type bridge, followed by bringing the bridge interface up with ip link set BRNAME up. In practice, the choice of method depends on the distribution and the networking stack in use.

Typical usage involves creating the bridge, enabling it, and then adding ports. For example, one can create a bridge named br0, bring it up, and then attach physical or virtual interfaces to it. Ports are added either with brctl addif BRNAME INTERFACE or by setting the interface’s master to BRNAME using ip link set INTERFACE master BRNAME. After ports are attached, IP configuration is usually applied to the bridge interface itself, or managed by a network manager that handles bridging.

Administrators may configure additional bridge options as needed, including port learning behavior, Spanning Tree Protocol settings, and firewall rules for bridged traffic. Proper kernel parameters and network manager configurations should be considered to ensure correct forwarding, security, and performance in the bridged environment.

See also: brctl, ip, iproute2, bridge utilities.