Linux Bridge Utilities For Linux

Linux Bridge Utilities is a bridge is a way to connect two Ethernet segments together in a protocol independent way. Packets are forwarded based on Ethernet address, rather than IP address (like a router). Since forwarding is done at Layer 2, all protocols can go transparently through a bridge.

The Linux bridge code implements a subset of the ANSI/IEEE 802.1d standard. [1]. The original Linux bridging was first done in Linux 2.2, then rewritten by Lennert Buytenhek. The code for bridging has been integrated into 2.4 and 2.6 kernel series.

Network cards

Before you start make sure both network cards are set up and working properly. Don't set the IP address, and don't let the startup scripts run DHCP on the ethernet interfaces either. The IP address needs to be set after the bridge has been configured.

The command ifconfig should show both network cards, and they should have be DOWN.

Module loading

In most cases, the bridge code is built as a module. If the module is configured and installed correctly, it will get automatically loaded on the first brctl command. If your bridge-utilities have been correctly built and your kernel and bridge-module are OK, then issuing a brctl should show a small command synopsis.