11.2.6. Network Bridge
/etc/sysconfig/network-scripts/
directory called ifcfg-brN
, replacing N with the number for the interface, such as 0
.
- The
DEVICE
directive is given an interface name as its argument in the formatbrN
, where N is replaced with the number of the interface. - The
TYPE
directive is given an argumentBridge
. This directive determines the device type and the argument is case sensitive. - The bridge interface configuration file now has the
IP
address and the physical interface has only a MAC address. - An extra directive,
DELAY=0
, is added to prevent the bridge from waiting while it monitors traffic, learns where hosts are located, and builds a table of MAC addresses on which to base its filtering decisions. The default delay of 15 seconds is not needed if no routing loops are possible. - The
NM_CONTROLLED=no
should be added to the Ethernet interface to prevent NetworkManager from altering the file. It can also be added to the bridge configuration file in case future versions of NetworkManager support bridge configuration.
IP
address:
Example 11.4. Sample ifcfg-br0 interface configuration file
DEVICE=br0 TYPE=Bridge IPADDR=192.168.1.1 NETMASK=255.255.255.0 ONBOOT=yes BOOTPROTO=none NM_CONTROLLED=no DELAY=0
/etc/sysconfig/network-scripts/ifcfg-ethX
, where X is a unique number corresponding to a specific interface, as follows:
Example 11.5. Sample ifcfg-ethX interface configuration file
DEVICE=ethX TYPE=Ethernet HWADDR=AA:BB:CC:DD:EE:FF BOOTPROTO=none ONBOOT=yes NM_CONTROLLED=no BRIDGE=br0
Note
DEVICE
directive, almost any interface name could be used as it does not determine the device type. Other commonly used names include tap
, dummy
and bond
for example. TYPE=Ethernet
is not strictly required. If the TYPE
directive is not set, the device is treated as an Ethernet device (unless its name explicitly matches a different interface configuration file.)
Warning
service network restart
11.2.6.1. Network Bridge with Bond
DEVICE=ethX TYPE=Ethernet USERCTL=no SLAVE=yes MASTER=bond0 BOOTPROTO=none HWADDR=AA:BB:CC:DD:EE:FF NM_CONTROLLED=no
Note
ethX
as the interface name is common practice but almost any name could be used. Names such as tap
, dummy
and bond
are commonly used.
/etc/sysconfig/network-scripts/ifcfg-bond0
, as follows:
DEVICE=bond0 ONBOOT=yes BONDING_OPTS='mode=1 miimon=100' BRIDGE=br0 NM_CONTROLLED=noFor further instructions and advice on configuring the bonding module and to view the list of bonding parameters, see Section 31.8.1, “Using Channel Bonding”.
/etc/sysconfig/network-scripts/ifcfg-br0
, as follows:
DEVICE=br0 ONBOOT=yes TYPE=Bridge IPADDR=192.168.1.1 NETMASK=255.255.255.0 NM_CONTROLLED=no

Figure 11.1. A network bridge consisting of two bonded Ethernet interfaces.
MASTER=bond0
directive. These point to the configuration file named /etc/sysconfig/network-scripts/ifcfg-bond0
, which contains the DEVICE=bond0
directive. This ifcfg-bond0
in turn points to the /etc/sysconfig/network-scripts/ifcfg-br0
configuration file, which contains the IP
address, and acts as an interface to the virtual networks inside the host.
root
in the following format: ifup device
~]# service network restart
11.2.6.2. Network Bridge with Bonded VLAN
- Ensure the bond and VLAN have been configured as outlined in Section 11.2.5, “Configuring a VLAN over a Bond”.
- Create the bridge's configuration file,
ifcfg-br0
:~]# vi /etc/sysconfig/network-scripts/ifcfg-br0 DEVICE=br0 ONBOOT=yes TYPE=Bridge IPADDR=192.168.10.1 NETMASK=255.255.255.0 NM_CONTROLLED=no
- Adjust the VLAN's configuration file,
ifcfg-bond0.192
from the earlier example, to use the newly createdbr0
as its master:~]# vi /etc/sysconfig/network-scripts/ifcfg-bond0.192 DEVICE=bond0.192 BOOTPROTO=none ONPARENT=yes #IPADDR=192.168.10.1 #NETMASK=255.255.255.0 VLAN=yes NM_CONTROLLED=no BRIDGE=br0
- To bring up the new or recently configured interfaces, issue a command as
root
in the following format:ifup device
Alternatively, restart the networking service, in order for the changes to take effect, as follows:~]#
service network restart