Softwarebridged

Softwarebridged, sometimes written as software bridging or software-bridged networking, is the practice of implementing network bridging entirely in software on general-purpose hardware rather than in dedicated network devices. At its core, a software bridge forwards frames at the data link layer between interfaces or virtual interfaces, effectively acting as a virtual Ethernet switch inside the host’s operating system or virtualization platform.

A software bridge learns which devices are reachable on each port by inspecting source MAC addresses and maintains a forwarding database. When a frame arrives, the bridge forwards it to the appropriate port or floods it if the destination is unknown. It may also participate in standard features such as VLAN tagging, spanning tree protocols to prevent loops, and security controls to limit who can connect to the bridge. Popular implementations include the Linux bridge subsystem (often managed via brctl or iproute2) and Open vSwitch, which provides advanced features for virtualized environments and software-defined networking.

Softwarebridged networking is widely used in virtual machine hosts, container platforms, and cloud environments to connect guests to each other and to physical networks without specialized hardware. It enables flexible network topologies, rapid provisioning, and easier integration with network virtualization technologies. However, it places forwarding workload on the host CPU and can incur higher latency and lower predictable throughput compared to hardware-accelerated bridging. Performance can be enhanced with tuning, NIC offloads, or accelerated data planes in platforms like Open vSwitch with DPDK.

In summary, softwarebridged networking offers flexible, cost-effective link-layer connectivity built in software, suitable for virtualized and SDN-enabled environments, with trade-offs in performance and complexity.