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What is Linux Bridge?

A software-based network switch in the Linux kernel that connects multiple network interfaces at Layer 2, enabling VM and container networking.

A Linux bridge operates like a physical network switch in software, forwarding Ethernet frames between connected interfaces based on MAC addresses. Bridges are fundamental to virtualization (KVM/QEMU VMs connect through bridges to reach the physical network) and container networking (Docker creates docker0 bridge by default). Configuration uses ip link and bridge commands or the legacy brctl tool. Bridges support STP (Spanning Tree Protocol) to prevent loops, VLAN filtering for traffic isolation, and can be combined with iptables for firewalling bridged traffic. Network namespaces connect to bridges via veth pairs.

Related Terms

Journald
The systemd journal daemon that collects and stores log data from services, the kernel, and boot messages in a structured binary format.
Procfs (/proc)
A virtual filesystem in Linux that provides an interface to kernel data structures, exposing process and system information as files.
Systemd
A system and service manager for Linux that initializes the system and manages services, logging, and more.
Crontab Syntax
The time specification format used in cron job scheduling, with five fields defining minute, hour, day of month, month, and day of week.
Systemctl
The primary command for managing systemd services, including starting, stopping, enabling, and checking service status.
Curl
A versatile command-line tool for transferring data using various network protocols, commonly used for API testing.
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