1. About Network Bridge

    A network bridge is a Link Layer device which forwards traffic between networks based on MAC addresses and is therefore also referred to as a Layer 2 device.

    It makes forwarding decisions based on tables of MAC addresses which it builds by learning what hosts are connected to each network. 

    A software bridge can be used within a Linux host in order to emulate a hardware 

bridge, for example in virtualization applications for sharing a NIC with one or more virtual NICs. 

Example： Sample ifcfg-br0 interface configuration file

DEVICE=br0

TYPE=Bridge

IPADDR=192.168.1.100

NETMASK=255.255.255.0

ONBOOT=yes

BOOTPROTO=none

NM_CONTROLLED=no

DELAY=0

Example：Sample ifcfg-eth0 interface configuration file

DEVICE=eth0

TYPE=Ethernet

HWADDR=08:00:27:72:C0:A0

BOOTPROTO=none

ONBOOT=yes

NM_CONTROLLED=no

BRIDGE=br0

Linux Network Bridge